The Australian Maritime Safety Authority has revealed imagery that could be of debris near the search zone for missing Malaysia Airlines flight MH370.

A merchant ship is steaming towards a spot in the southern Indian Ocean where two large objects that might be parts of a missing Malaysia Airlines plane have been identified.

But while the Australian Maritime Safety Authority (AMSA) says the objects, captured on satellite imagery, are their best lead so far, they caution that they might prove to have nothing to do with flight MH370.

MH370 disappeared hours after leaving Kuala Lumpur for Beijing early on Saturday March 8 with 239 people on board.

AMSA is coordinating a search for the plane in the southern Indian Ocean.

John Young, emergency response division general manager at AMSA, says the objects, one believed to be about 24 metres across, are some 2300km southwest of Perth and will be difficult to locate.

“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,” he said.

“AMSA is doing its level best to find anyone that might have survived,” he said when asked what advice he had for families of those on the missing flight.

An RAAF aircraft arrived at the area just before 2pm (AEDT) and three more military aircraft, including two from the United States and New Zealand, are expected to reach the area later on Thursday.

An Australian Hercules will drop marker buoys in the area highlighted by the satellite imagery.

A merchant ship that responded to a shipping broadcast issued by Rescue Coordination Australia on Monday is expected to arrive in the area about 6pm (AEDT).

Mr Young said the marker buoys will provide an ongoing reference point if the task of relocating the objects becomes protracted.

In AMSA’S experience there was usually debris floating in that area, but on this occasion the size, and the fact that there were a number, made it worth looking at, he said.

He also cautioned against any hasty expectations of an outcome of the search because of unfavourable weather conditions.

“We may get a sighting, we may not. We may get it tomorrow, we may not,” he said.

“But we will continue to do this until we locate those objects or we are convinced that we cannot find them.”

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.