The hunt for missing Malaysia Airlines Flight MH370 is to shift further south in the Indian Ocean.

Australian authorities today announced the new phase of the long, costly and so far fruitless search.

The Boeing 777, carrying 239 passengers and crew, disappeared on 8 March 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, about 1,600km off the northwest coast of Australia, and the search area would have to be expanded.

The search for the missing plane is already the most expensive in aviation history.

Australia's Deputy Prime Minister Warren Truss said that the new priority area is still focused on the same arc, where the aircraft last communicated with satellite.

He added: "We are now shifting our attention to an area further south along the arc."

Mr 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 most remote 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," Mr Truss told reporters in Canberra.

Two vessels, one Chinese and one from Dutch engineering company Fugro, are currently mapping the sea floor 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 about 60, of ocean at a cost of A$60 million (€41m) or more.