Survivors of the MV Rabaul sinking of the east coast of Papua New Guinea say they battled to stay alive after the ferry overturned in rough seas.

As many as 100 people remain unaccounted for after the 22-year-old Japanese-built ferry sank near the end of its 20-hour, 290-nautical mile journey between Kimbe and PNG's second largest city, Lae, on Thursday morning (AEDT).

There were 350 passengers and 12 crew on board.

"We were in the top deck, first class,'' said Alice Kakamara, 30, from her hospital bed in Lae's Angau hospital.


"The sea was really rough, windy, big waves. The boat tilted once, then twice then three times and it went over.

"There was oil everywhere.''

Ms Kakamara is one of seven people brought to Angau hospital after the accident.

She is among four being treated after, according to doctors, inhaling toxic substances during the clamour to escape the wreck.

Another two patients have what is being described as serious chest trauma and another has psychological problems.

Ms Kakamara says she almost gave up during the ordeal, but was saved by her 11-year-old nephew William who pleaded with her to keep going.

"He told me not to give up,'' she said.

"We found a lifeboat, but it was sinking. I put him in another (boat) and I haven't seen him, but my relatives say he is now with them.''

Another man, Wakei, said he was searching for four members of his family who have not yet been accounted four.

He said his aunt, Pauline Bani, and her children were missing.

"I came here to find them, but I want to check if another ship is coming in,'' he said.

The owners, PNG-based Rabaul Shipping Company, confirmed 350 passengers and 12 crew were onboard.

"We are stunned and utterly devastated by what has happened,'' managing director Peter Sharp said in a statement.

"We acknowledge that this has caused tremendous suffering. Our condolences go to the loved ones of those affected.

"While we are trying to comprehend the terrible nature of the accident, we are also staying focused on helping authorities as the search and rescue operation unfolds.''

At the Lae Disaster Management centre, where most of the survivors gathered, director Charlie Masang told reporters that Ausaid, the Red Cross and the Salvation Army have all provided food and bedding to the survivors.

Australia has also given its assistance.

The Australian Maritime Safety Authority (AMSA) arranged for ships in the area to conduct rescues and for aircraft to fly over the area.

The aircraft assisted with dropping rescue equipment, including life rafts.

The Australian High Commission in Port Moresby is still trying to confirm whether any Australians were on the vessel.

Australia's High Commissioner to PNG, Ian Kemish, could not say exactly what caused the disaster but believed conditions may have played a part.

"I think it's a fair bet that the very severe weather that's being experienced in some parts of Papua New Guinea played a role, but I can't say much more about the cause of the sinking beyond that at this stage,'' he told ABC TV.