Italy's civil protection agency says the earthquake death toll has risen to 247, with hundreds more injured or unaccounted for.
The shallow 6.2 magnitude quake struck 10km southeast of Norcia, a historic tourist town in southeastern Umbria, central Italy on Wednesday morning.
The quake saw buildings reduced to dust in the area straddling the regions of Umbria, Marche and Lazio.
Rescue workers are racing against the clock to find people trapped under rubble, but hope is diminishing as reports of voices from under collapsed buildings drop off.
One man working on the recovery mission in the hard hit town of Amatrice told the Nine Network the once beautiful community was now "like Syria".
"It is a total war zone in there," the rescuer said.
The quake hit about 3.30am local time when many were asleep, devastating whole towns across the region. A family of four believed to include a nine-year-old and an eight-month old baby, is among the dead, according to the mayor of Accumoli, Stefano Petrucci.
"Four people are under the rubble, but they are not showing any sign of life. Two parents and two children," he said.
Locals, paramedics, police and rescue workers joined forces on Wednesday to address the devastation that affected nearly 70 hamlets across the countryside.
"We see that the situation is even more dreadful than we feared with buildings collapsed, people trapped under the rubble and no sound of life," the mayor said.
Civil protection worker Andrew Gentili told AP early efforts were directed at finding people trapped under rubble.
"We need chainsaws, shears to cut iron bars, and jacks to remove beams: everything, we need everything," she said.
Offers of help have flooded in from other European allies and Italians have taken to social media to share their stories and offer solidarity with victims under the hashtags #terremoto and #PrayforItaly.
The Australian embassy in Rome is working to determine whether any Australians were involved and have urged those trying to find information to contact the Department of Foreign Affairs' 24-hour centre.
'EVERYTHING IS RUBBLE'
Local photographer Emiliano Grillotti told the BBC "everything is rubble" in Amatrice.
"Amatrice is totally in ruins. One of the most beautiful villages in the whole of Italy now doesn't exist. Everything is rubble, only rubble."
Prime Minister Matteo Renzi cancelled a planned trip to France for a meeting with European Socialist leaders and other engagements to oversee the response to the disaster.
"The situation is dramatic, there are many dead," he said.
Renzi thanked the tireless rescue workers and vowed a sustained national effort to find any survivors and assist the injured and homeless. "No family, no city, no hamlet will be left alone," he said.
The quake was felt as far away as Rome, about 150km away from the epicentre, as homes in the historic centre swayed.
The Italian earthquake institute (INGV) reported 60 aftershocks in the four hours following the initial quake, the strongest measuring 5.5.
The worst damage was suffered by Pescara del Tronto, a hamlet near Arquata in the Marche region, which civil protection workers described as having been virtually razed.
Ten bodies had been recovered there by midmorning. Among them, an elderly couple killed as their home collapsed.
The death toll is expected to rise as rescue crews reach homes in harder-to-reach villages around the area. They are also facing power outages and ruptured gas lines.
Arquata mayor Aleandro Petrucci said Pescara had "just completely disintegrated". The city of Amatrice, near the epicentre, was reportedly also "destroyed".
Amatrice mayor Sergio Pirozzi said "half of the city disappeared". Rocks and metal tumbled onto the streets and dazed residents huddled in piazzas as aftershocks continued into the early morning hours.
Amatrice resident Maria Gianni said her "whole ceiling fell but did not hit me".
"I just managed to put a pillow on my head and I wasn't hit luckily, just slightly injured my leg," she said.
Another woman, sitting in front of her destroyed home with a blanket over her shoulders, said she didn't know what had come of her loved ones.
"It was one of the most beautiful towns of Italy and now there's nothing left," she said, too distraught to give her name. "I don't know what we'll do."
According to Reuters, the town's hospital had been badly damaged by the quake, with patients moved into the streets.
Mr Pirozzi said the quake was a "tragedy" and that some of his constituents are trapped under the rubble.
"The town doesn't exist anymore," Mr Pirozzi said. "The ancient doors have come down. We need help from the civic protection.
"It's all rubble, it's a tragedy.
"The aim now is to save as many lives as possible. There are voices under the rubble, we have to save the people there."
PEAK SUMMER SEASON
Amatrice was packed with visitors at the peak of the summer season when the quake struck, destroying the picturesque hilltop village's main street.
The town is famous as a beauty spot and is a popular holiday destination for Romans seeking cool mountain air at the height of the summer.
Witnesses told Italian media that many buildings had collapsed in villages close to the epicentre of the quake near the town of Norcia in the region of Umbria.
People reportedly ran into streets in central Umbria and Le Marche, according to state-run RAI radio.
Flavio Maccarone, 35, of the Ascoli Piceno province, told news.com.au the "aftershocks keep going so we are outside praying that it stops soon".
"We feel terrified," Mr Maccarone said.
"It feels like we are experiencing again the Perugia quake in 1997 or the Aquila quake in 2009.
"It never ends. We cannot sleep in peace. We are trying to stay calm but it is hard. Our poor people and all our history is damaged.
"You can't control it. There is nothing you can do. We feel hopeless. The quake affected such a wide area it is hard to send targeted help."
Mr Maccarone said he had fears for his friend in Amatrice, a mountain village in neighbouring Lazio, with a population of just a few thousand people. The village was packed with visitors at the peak of the summer season.
"I keep calling him but he is not answering. I hope it is just a bad signal," Mr Maccarone said.
"Half the country needs help ... how do you do that?"
As dawn broke on Wednesday, residents with shovels and emergency workers with bulldozers were beginning to try to reach people trapped under the debris and clear blocked roads.
The Repubblica newspaper reported that at least one bridge had collapsed, making access for emergency services difficult.
The AGI news agency reported there was "a landslide on one road (and) a bridge is about to collapse on the other one".
Mr Pirozzi said the access roads to the town "are isolated".
"I've issued an appeal to free up the roads," he said.
"Half the village is no more, we have people buried under the rubble. I fear they are dead. We have room for rescue helicopters but the priority is to clear the streets. We are working without lights".
Alessandro Mazzilli, of the Alpine emergency service of Rieti, said: "There are problems in Amatrice, we are heading that way."
"Apparently houses have collapsed now, but I am not there yet so can't confirm," he said.
"The quake has been felt throughout the whole of central Italy - even in the Adriatic Sea."
Pope Francis interrupted his weekly audience in St Peter's square to express his shock at the news.
"To hear the mayor of Amatrice say his village no longer exists and knowing that there are children among the victims, is very upsetting for me," he said.
Social media users have taken to Twitter to post photos of the devastation.
United States Geological Service projections has predicted there will be casualties in towns close to the epicentre. These include Accumoli (less than 1000 residents), Norcia (5000), Maltignano (3000), Amatrice (3000), Cascia (3000) and Cittareale (less than 1000).
USGS's PAGER system, which predicts the impact of earthquakes, has issued a red alert - suggesting significant casualties and damage based on previous quake data.
RACE TO RESPOND
Mr Pirozzi told state-run RAI radio and Sky TG24 that he needs heavy equipment to clear rubble-clogged streets to get to the injured.
Asked if there were any dead he said: "Look there are houses that aren't here anymore. I hope we get some help."
Three helicopters and six vehicles are on their way to the affected region, in addition to rescue efforts by Italy Civil Protection, the Lazio regional government said on their Facebook page.
Rescuers have already pulled several people - survivors and the dead - from the rubble.
Rainews24 channel reported that rescue workers called Amatrice residents' cellphones, and tried to get to those who answered. If there was no answer, rescuers moved on to the next person.
CNN reported that Tommaso della Longa, a spokesman for the Red Cross, said the images coming out of Amatrice are grim.
"The picture we got from our delegate in Amatrice are telling us a terrible story of a small city almost completely destroyed," he said. "The situation is difficult at the moment."
The priority is to find survivors, he said.
"These areas are in central Italy and are in middle of mountains and valleys," he said. "There are small houses in the middle of the valley that are completely alone and they need help. It'll take some time to reach them."
Prime Minister Matteo Renzi's spokesman said on Twitter that the government was in touch with the country's civil protection agency, which said the earthquake was "severe".
Italy's Red Cross is reporting that at least one bridge into the mountainous area is on the point of collapse.
The spokesman for the Italian fire department, Luca Cari, said they had received reports of buildings being damaged, but had no further details.
"It was the worst (quake) of my life" Matteo Berlenga told Reuters after leaving his house near Gubbio in the central Italian region of Umbria when the earthquake struck.
A resident of the Rieti region, which is between Rome and the epicentre of the quake, told the Rainews24 channel that she and most of her neighbours had come out onto the street after feeling "very strong shaking".
ITALY IS PRONE TO NATURAL DISASTERS
The Italy earthquake has occurred 1,937 years to the day since Mt Vesuvius erupted in 79AD and destroyed Pompeii and Herculaneum - one of the most catastrophic volcanic eruptions in European history.
Italy sits on two fault lines, making it one of the most seismically active countries in Europe.
A 2009, 6.3-magnitude earthquake in the Aquila region, about 90km south of the latest quake, which was also felt in the Italian capital, left more than 300 dead.
That disaster led to lengthy recriminations over lax building controls and the failure of authorities to warn residents that a quake could be imminent.
Another quake hit the northern Emilia Romagna region in May 2012, when two violent shocks 10 days apart left 23 people dead and 14,000 others homeless.
The most deadly since the start of the 20th century came in 1908, when an earthquake followed by a tsunami killed an estimated 80,000 people in the southern regions of Reggio Calabria and Sicily.