Australia is taking on responsibility for searching a major section of the Southern Ocean as part of an international effort to find missing Malaysia Airlines flight MH370.

Prime Minister Tony Abbott on Monday referred to the incident as an “unfathomed mystery” when telling federal parliament he had recently spoken with his Malaysian counterpart Najib Razak.

“He asked that Australia take responsibility for the search in the southern vector, which the Malaysian authorities now think was one possible flight path for this ill-fated aircraft,” Mr Abbott said.

Mr Razak also accepted an offer of additional Australian maritime surveillance resources.

The countries’ defence chiefs have also been in contact to determine Australia’s role, Mr Abbott said.

“Australia will do its duty in this matter … to ensure that our search and rescue responsibilities are maintained and upheld,” he said.

The aircraft was carrying 239 people – including six Australians – when it disappeared on March 8 during a flight bound for Beijing.

US serviceman on the P-8A Poseidon which is part of the search effort.

Now 25 countries are searching for the missing airliner as authorities investigate the possibility of a hijacking.

Opposition Leader Bill Shorten said Labor supported the government’s efforts to increase search assistance.

Over the weekend there was speculation of a political motive and suggestions the senior pilot had been influenced by radical politics.

This was widely denied however, with other pilots vouching for his good character.

While there have been suggestions that the plane would have ditched in the Indian Ocean, there are also theories suggesting the aircraft headed north-west into central Asia.

There has been criticism of the Malaysian authorities, notably that they have been slow to confirm the facts of the matter and that they could have acted faster.