Malaysian PM Visits Australian Plane Search HQ

Malaysian Prime Minister Najib Razak has described the search for missing flight MH370 as a "gargantuan task" but insisted there will be no let up for the sake of the victims' families.

Mr Razak is visiting the airbase near Perth, Australia, where the search is being co-ordinated.

He joined Australian Prime Minister Tony Abbott as they watched planes fly out on their daily mission to the Indian Ocean.

Eight aircraft and nine ships are involved in Thursday's operation, which has faced tough weather conditions west of Perth.

"We owe it to the grieving families to ... give them comfort and closure to this rather tragic event and the world expects us to do our level best," said the Malaysian prime minister.

"We want to find answers. We want to provide comfort to the families and we will not rest until answers are indeed found."

Mr Abbott said Australia was "throwing everything at it" to find the Malaysia Airlines plane, which disappeared on its way from Kuala Lumpur to Beijing on March 8.

The search area shifted slightly north on Thursday, said the Australian premier.

Mr Abbott added: "This is most probably the most difficult search ever undertaken ... but I can assure people that the best brains in the world are working on this.

"We are putting the jigsaw together and every day we have a higher degree of confidence that we know more about what happened to this ill-fated flight."

Sky News' James Matthews, at Pearce airbase, said the two men were "speaking the language of the long-term" with no immediate end in sight for the mystery.

British Navy submarine HMS Tireless boosted the search on Wednesday as the hunt for the crucial black box counts down. The device's battery is likely to have only a few days of power left to transmit its signal.

Royal Navy survey ship HMS Echo is also in the area.

Family members of the 227 passengers have repeatedly accused the authorities of lying to them and holding back information.

Multiple sightings of possible debris have so far failed to turn up any sign of the aircraft, which investigators say - beyond reasonable doubt - went down in the Indian Ocean.