PERTH (AFP) - Malaysia will not rest until it can give answers to the distraught families of those on board missing Flight MH370, Prime Minister Najib Razak said on Thursday, admitting the search was a "gargantuan" challenge.

International efforts to find any sign of the Malaysia Airlines plane which vanished on March 8 have so far failed, but search coordinator Australia says there are no imminent plans to abandon the operation.

"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," Mr Najib said as he toured the search base in Perth.

"We want to find answers. We want to provide comfort to the families and we will not rest until answers are indeed found." Najib said the hunt for the Boeing 777 was probably the largest mission to locate an aircraft ever staged and he was confident it would provide answers to the baffling mystery.

"I am very confident with the level of professionalism... that indeed in due time we will provide a closure to this event, on this tragedy," he said as he thanked those involved in "this gargantuan task".

"I know it is a daunting task in very inclement weather, in very challenging circumstances and Malaysia is indeed grateful for your courage and your commitment."

Malaysia believes the jet carrying 239 people went down in the southern Indian Ocean off Perth. Despite extensive scouring of the remote area, no debris that would indicate a crash site has so far been found.

Kuala Lumpur's handling of the crisis has been widely criticised, especially by relatives of the 153 Chinese nationals aboard.