Australian Prime Minister Tony Abbott on Monday vowed and assured relatives of the 239 passengers aboard the missing Malaysia Airlines MH370 that the search and retrieval operations for the mystery plane has no time cap.

"I'm certainly not putting a time limit on it," Reuters quoted Mr Abbott tell reporters in Perth after meeting the flight search crew at Pearce airbase.

He also pointed out that the intensity for the search and the magnitude of operations is "increasing, not decreasing," sending a firm commitment to the aggrieved families that the global operations understand their frustrations to already locate the plane that's been more than three weeks missing since March 8.

To date, the international search and retrieval has enlisted the participation of Australia, the United States, New Zealand, Malaysia, China, Japan and Korea, among others.

At least 20 aircraft and ships resumed searching a massive area in the Indian Ocean on Monday, some 2,000km west of Perth, Australia.

"If you compare this to Air France flight 447, we had much better positional information of where that aircraft went into the water," US Navy Captain Mark Matthews said on Sunday.

All because the location where authorities are now focusing, roughly the size of Poland or New Mexico, "is located just outside of what we call the garbage patches," Erik van Sebille, an oceanographer at the University of New South Wales said.

Malaysia earlier announced that with the aid of British spy agency MI6 and US Central Intelligence Agency (CIA), it confirmed the plane had crashed in the southern Indian Ocean.

The US intelligence has ruled out terror links with the missing Malaysia Airlines MH370, based on the involvement of MI6 and the CIA. Speculations mounted the airliner went missing due to a criminal act rather than mechanical failure.

"So far, there's been none," Senator Dianne Feinstein, chairperson of the Senate Intelligence Committee, told CNN's Candy Crowley Sunday on 'State of the Union' programme. "There's speculation, but there's nothing."