Norwegian car carrier Hoegh St Petersburg has reached the area in the southern Indian Ocean off Australia where two floating objects, suspected to be debris from the missing Malaysian jetliner, were spotted, the ship owner's said on Thursday.

The car carrier was on its way from Madagascar to Melbourne when it got a request from Australian authorities to assist in investigating the objects spotted by satellite four days ago in one of the remotest parts of the globe, around 2,500 km (1,500 miles) southwest of Perth.

Earlier reports said aircraft and ships ploughed through bad weather on Thursday in search of floating objects in remote seas off Australia that Malaysia's government called a "credible lead" in the trans-continental hunt for a jetliner missing for 12 days.

The large objects, which Australian officials said were spotted by satellite four days ago in one of the remotest parts of the globe, are the most promising lead in days as searchers scour a vast area for the lost plane with 239 people on board.

Officials cautioned it could take several days to confirm if they were parts of the Malaysia Airlines Boeing 777, and Malaysia's government said the search would continue elsewhere despite the possible sighting in the southern Indian Ocean.

The area where the objects were spotted is around 2,500 km (1,500 miles) southwest of Perth in western Australia.

"Yesterday I said that we wanted to reduce the area of the search. We now have a credible lead," Malaysian Transport Minister Hishammuddin Hussein told reporters in Kuala Lumpur.

"There remains much work to be done to deploy the assets. This work will continue overnight."

Hishammuddin said the information on the objects received from Australia had been "corroborated to a certain extent" by other satellites, making it more credible than previous leads.

The larger of the objects measured up to 24 metres (79 ft), long and appeared to be floating in water several thousand metres deep, Australian officials said. The second object was about five metres (16 feet) long. Arrows on the images pointed to two indistinct objects apparently bobbing in the water.

"It's credible enough to divert the research to this area on the basis it provides a promising lead to what might be wreckage from the debris field," Royal Australian Air Force Air Commodore John McGarry told a news conference in Canberra.

No confirmed wreckage from Flight MH370 has been found since it vanished from air traffic control screens off Malaysia's east coast early on March 8, less than an hour after taking off from Kuala Lumpur for Beijing.

Another official in Malaysia said investigators were "hopeful but cautious" about the Australian discovery.

The satellite images, provided by US company DigitalGlobe, are stamped with a record date of March 16, meaning that the possible debris could by now have drifted far from the original site.

Australian officials said an aircraft had dropped a series of marker buoys in the area, which will provide information about currents to assist in calculating the latest location.

The captain of the first Australian air force AP-3C Orion plane to return from the search area described the weather conditions as "extremely bad" with rough seas and high winds, and said there was no sign of any objects.

"The weather conditions were such that we were unable to see for very much of the flight today but the other aircraft that are searching, they may have better conditions," Royal Australian Air Force Flight Lieutenant Chris Birrer told reporters.

At least one aircraft, a Royal New Zealand Air Force Orion, was still in the search area, while other aircraft including a US Navy P-8 Poseidon were returning to Perth, according to the Australian Maritime Safety Authority (AMSA).

A Royal Australian Navy ship equipped to recover any objects was also en route, but was still "some days away", Young said. - Reuters