MH370: China president 'devastated' by plane mystery

"As you can understand he is devastated, as are so many people in China, as is (Malaysian) Prime Minister Najib (Razak) by all of this," Abbott said following the call on Thursday evening, which came after Australia detected possible debris from the plane.

"This has been a gut-wrenching business for so many people."

Of the 239 passengers and crew on the Kuala Lumpur-Beijing flight that vanished on March 8, 153 were Chinese citizens.

Chinese state media said Xi described the flight's disappearance as a "calamity" during the talks with Abbott, who is in Papua New Guinea.

"Since the plane lost contact, our hearts have been with the lives of the people from different countries on board the plane," Xi said, according to state-run Xinhua news agency.

The Malaysian government believes the jet was deliberately diverted and flew for several hours after leaving its scheduled flight path -- either north towards Central Asia, or towards the southern Indian Ocean.

Authorities in Kuala Lumpur on Monday asked Canberra to take responsibility for the "southern vector", and on Thursday Australian officials said two objects had been sighted by satellite in the remote southern Indian Ocean.

Sorties by four planes from Australia, New Zealand and the United States to the area some 2,500 kilometres southwest of Perth on Thursday failed to find anything, hampered by low cloud, with more missions underway Friday.

A Norwegian merchant ship was scouring the search area and Australia's HMAS Success, which is capable of retrieving any wreckage, was steaming to the scene.

China's state broadcaster CCTV said on a verified microblog account that three Chinese navy vessels were also heading for where the possible debris was spotted, along with Chinese icebreaker Xuelong, which was in port in Fremantle in western Australia.

Abbott said Australia was doing all it could to resolve the mystery.

"We've been throwing everything we've got at that area to try to learn more about what this debris might be," he said.

"It could just be a container that has fallen off a ship, we just don't know.

"But we owe it to the families and the friends and the loved ones of the almost 240 people on flight MH370 to do everything we can to try to resolve what is as yet an extraordinary riddle."