Prime Minister John Key tonight confirmed an Orion had been deployed to the search area and could play a key role.
"It's hard to believe the plane, if it is the plane, is actually there, given it's so far off course and in a completely different direction."
He said New Zealand would also be ready to offer more help if required, such as planes, naval equipment and personnel for any recovery effort.
"There are other assets we can deploy. If this really is the wreckage then it is relatively close to New Zealand.
"This whole thing has been extremely unusual. There is so much we don't know. One good bit of news is that if they do locate the wreckage I guess there's a chance they will get much better information about what actually happened. The search will then be for the black box. How hard that will be to find in that kind of water, who knows?"
Mr Key said he had discussed Malaysia's response with China's President Xi Jinping.
Mr Key said it was hard to judge Malaysia for its response.
New Zealand had stayed in contact and he believed Malaysia had given the best information they could, but had been very uncertain about what was happening.
He expected questions of Malaysia's handling would be addressed after the plane was found and it was better known what had happened.
Authorities should know something definite on the possible discovery of debris within "two or three days'', Australian Defence Minister David Johnston said.
ABC News in the US had reported that a flight crew scouring the southern Indian Ocean had been getting radar hits of "significant size," indicating something lurking below the water's surface, but the US Navy said this was not linked to the Australian announcement.
John Young of the Australian Maritime Safety Authority (AMSA) was cautious not to raise hopes earlier tonight, saying the satellite imagery shows "a sort of blob" with no features to distinguish it as aircraft fragments.
"It's probably the best lead we have right now but we have to get there, find them, see them, assess them to know whether it's really meaningful or not," the emergency response division manager said.
Read more:
• Relatives accuse authorities of 'hiding the truth'
• Editorial: Malaysia falls short in lost jet mystery
• US pilot's fire theory
Water in the area is thousands of metres deep and searchers are battling poor visibility, with last light due about midnight (AEDT) on Thursday.
"Every lead is a hope," Malaysian Transport Minister Hishammuddin Hussein told reporters in Kuala Lumpur.
"This time I just hope that it is a positive development."
Australia has been co-ordinating the search operation in the southern Indian Ocean, which is based on calculations by United States experts who have analysed MH370's fuel range.
If the debris belongs to the aircraft, it indicates MH370 ended up thousands of kilometres from its planned destination, raising further questions about why it changed course.
But the priority for AMSA remains identifying the bobbing objects.
It is not uncommon to find floating debris, including shipping containers that have been washed overboard, Mr Young said.
Video: Possible MH370 objects spotted in water
"On this particular occasion, the size and the fact that there are a number located in the sea at the same area really makes it worth looking at."
An RAAF C-130 Hercules has dropped marker buoys at the location, and military aircraft from Australia, New Zealand and the US are combing the area.
A merchant ship was due to reach the area by 6pm (AEDT).
"They will be difficult to find. They might not be associated with the aircraft and we have plenty of experience of that in other searches," Mr Young said.
The search area is a long way from the Australian mainland and once aircraft reach the location, they have about only two hours of fuel before having to return to base.
Day three search area. Image / AMSA
Asked about his message to the family and friends of people on board flight MH370, Mr Young said Australia would continue to search until it found something.
"AMSA is doing its level best to find anyone who may have survived," he said.
Australia is sharing its information with 25 other countries involved in the search operation, and Prime Minister Tony Abbott confirmed on Thursday he had spoken to his Malaysian counterpart about the latest update.
Unfavourable weather may hinder the search.
"Weather conditions are moderate ... and poor visibility has been reported," an AMSA spokesman said.
"This will hamper both air and satellite efforts."
Day three search area. Image / AMSA
Prime Minister Tony Abbott says he has informed Malaysian Prime Minister Najib Razak of the developments.
But he also warned against drawing any premature conclusions or hopes on the search.
"We must keep in mind the task of locating these objects will be extremely difficult and it may turn out that they are not related to the search for flight MH370,'' Mr Abbott said.
Malaysian Transport Minister Hishammuddin Hussein says the lead gives reason for hope, but stressed the need to verify the claim.
"We have been very consistent. We want to verify, we want to corroborate,'' he told reporters on Thursday at Kuala Lumpur International Airport.
Watch: Relatives furious over Malaysian plane search
But this is the first time that possible objects have been spotted since the search area was massively expanded into two corridors, one stretching from northern Thailand into Central Asia and the other from the Strait of Malacca down to southern reaches of the Indian Ocean.
Earlier today, President Barack Obama said finding out what happened to the missing Malaysia Airlines plane was a top US priority.
Obama said every available US resource is aiding the search, including the FBI, the National Transportation Safety Board and others who deal with aviation.
Obama says he wants the families of the 239 missing people on the plane to know the US will keep working "to see if we can get to the bottom of this."
In his first public comments on the disappearance, Obama added that finding the plane will take time because the search area is so vast.
He commented Wednesday during an interview with Dallas-Fort Worth television station KDFW.
FBI joins search
The FBI joined forces with Malaysian authorities in analysing deleted data on a flight simulator belonging to the pilot of the missing Malaysia Airlines plane.
Watch more:
• Malaysia: Files deleted from flight simulator
• Australia, US launch search for jet
• Search area for jet 'big as Australia'
Files containing records of flight simulations were deleted February 3 from the device found in the home of the Malaysia Airlines pilot, Capt. Zaharie Ahmad Shah, Malaysian police chief Khalid Abu said.
It was not immediately clear whether investigators thought that deleting the files was unusual.
The files might hold signs of unusual flight paths that could help explain where the missing plane went. Then again, the files could have been deleted simply to clear memory for other material.
A man prays during an interfaith event for the missing jet in Kuala Lumpur. Photo / AP
Defence Minister Hishammuddin Hussein told a news conference that Zaharie is considered innocent until proven guilty. He said members of the pilot's family are cooperating in the investigation.
Zaharie was known to some within the online world of flight simulation enthusiasts.
In a post on one forum, the CEO of flight simulation software company PMDG wrote that Zaharie was a customer who "had developed an online presence in which he dedicated many hours of his time to promoting the enjoyment of flying generally, and flight simulation specifically."
The company CEO, Robert Randazzo, could not be reached directly for comment, but the publisher of the popular forum AVSIM Online, Tom Allensworth, confirmed that the post was from Randazzo.
A US official, speaking on condition of anonymity because the official was not authorized to discuss the ongoing investigation by name, said the FBI has been asked to analyze the deleted simulator files.
US Attorney General Eric Holder said in Washington that the FBI was working with Malaysian authorities.
"At this point, I don't think we have any theories," Holder said.
Flight 370 disappeared March 8 on a night flight from Kuala Lumpur to Beijing. Malaysian authorities have not ruled out any possible explanations, but have said the evidence so far suggests the flight was deliberately turned back across Malaysia to the Strait of Malacca, with its communications systems disabled. They are unsure what happened next and why.
Photo / AP
Investigators have identified two giant arcs of territory spanning the possible positions of the plane about 7 hours after takeoff, based on its last faint signal to a satellite an hourly "handshake" signal that continues even when communications are switched off. The arcs stretch up as far as Kazakhstan in central Asia and down deep into the southern Indian Ocean.
Police are considering the possibility of hijacking, sabotage, terrorism or issues related to the mental health of the pilots or anyone else on board, and have asked for background checks from abroad on all foreign passengers.
Hishammuddin said such checks have been received for all the foreigners except those from Ukraine and Russia which account for three passengers. "So far, no information of significance on any passengers has been found," he said.
The 53-year-old pilot joined Malaysia Airlines in 1981 and had more than 18,000 hours of flight experience. People who knew Zaharie from his involvement in opposition political circles in Malaysia and other areas of his life have described him as sociable, humble, caring and dedicated to his job.
The crisis has exposed the lack of a failsafe way of tracking modern passenger planes on which data transmission systems and transponders which make them visible to civilian radar have been severed. At enormous cost, 26 countries are helping Malaysia look for the plane.
Families' anger boils over
A Chinese relative of a passenger aboard the missing jet protests before a press conference at a hotel in Sepang, Malaysia. Photo / AP
The anguish of relatives of the 239 people on Flight 370 boiled over today at a briefing near Kuala Lumpur's airport.
Two Chinese women who shouted at Malaysian authorities and unfurled a banner accusing officials of "hiding the truth" were removed from the room. In a heart-wrenching scene, one woman screamed in sorrow as she was dragged away.
"I want you to help me to find my son! I want to see my son!" one of the two unidentified women said. "We have been here for 10 days."
At a hotel near the Kuala Lumpur airport, one of the Chinese women who was removed from the room displayed a banner that said, in part, "We are against the Malaysian government for hiding the truth." She later expressed frustration with officials.
"We launch our demands every day but to no answer, and they tell me to come back the next day," she said. "No answer, every day."
The father of passenger Pushpanathan Subramaniam said in an interview that the wait was "really too much."
"I don't know why it is taking so long for so many people to find the plane. It's 12 days," said 60-year-old Subaramaniam Gurusamy from his home on the outskirts of Kuala Lumpur. His 34-year-old son, Pushpanathan, was on the flight to Beijing for a work trip.
"He's the one son I have," Subaramaniam said.
Hishammuddin said a delegation of Malaysian government officials, diplomats, air force and civil aviation officials will head to Beijing where many of the passengers' relatives are gathered to brief the next of kin on the status of the search.
Aircraft from Australia, the US and New Zealand searched an area stretching across 305,000 square kilometers (117,000 square miles) of the Indian Ocean, about 2,600 kilometers (1,600 miles) southwest of Perth, on Australia's west coast. Merchant ships were also asked to look for any trace of the plane.
China has said it was reviewing radar data and deployed 21 satellites to search the northern corridor, although it is considered less likely that the plane could have taken that route without being detected by military radar systems of the countries in that region.
Indonesian defence Minister Purnomo Yusgiantoro said Indonesia military radar didn't pick up any signs of Flight 370 on the day the plane went missing. He said Malaysia had asked Indonesia to intensify the search in its assigned zone in the Indian Ocean west of Sumatra, but said his air force was strained in the task.
"We will do our utmost. We will do our best. But you do have to understand our limitations," Purnomo said.
- AP and AAP
