The hunt for missing Malaysia Airlines Flight MH370 will shift further south in the Indian Ocean, Australian authorities said on Thursday, ushering in yet another new phase of the long, costly and so far fruitless search.

The Boeing 777, carrying 239 passengers and crew, disappeared on March 8 shortly after taking off from Kuala Lumpur bound for Beijing.

Investigators say what little evidence they have to work with suggests the plane was deliberately diverted thousands of kilometres from its scheduled route before eventually plunging into the Indian Ocean.

The search was narrowed in April after a series of acoustic pings thought to be from the plane's black box recorders were heard along a final arc where analysis of satellite data put its last location.

But a month later, officials conceded the wreckage was not in that concentrated area, some 1,600 kilometres off the northwest coast of Australia, and the search area would have to be expanded.

"The new priority area is still focused on the seventh arc, where the aircraft last communicated with satellite. We are now shifting our attention to an area further south along the arc," Australian Deputy Prime Minister Warren Truss said.

Malaysia Airlines MH370 new search zone

In this image released by the Australian government Thursday, the new priority search area within the defined arc - where the jet last communicated with satellites - is shown in orange. The total search zone encompasses an area of nearly 60,000 square kilometres. (Australian Transport Safety Bureau)

Truss said the new priority search area was determined after a review of satellite data and early radar information as the plane suddenly diverted across the Malaysian peninsular and headed south into one of the remotest areas of the planet.

"It is highly, highly likely that the aircraft was on autopilot otherwise it could not have followed the orderly path that has been identified through the satellite sightings," Truss told reporters in Canberra.

Two vessels, one Chinese and one from Dutch engineering company Fugro are currently mapping the seafloor along the arc, where depths exceed 5,000 metres in parts.

The next phase of the search mission is expected to start in August and take a year, covering some 60,000 square kilometres of ocean at a cost of $56 million or more. The search is already the most expensive in aviation history.