"Based on the accumulation of the evidence, the Malaysian government has declared that flight MH370 was lost in the Southern Indian Ocean and all on board have perished," Abbott said while speaking to members of parliament today.
He said a considerable amount of debris had been sighted in the area where the flight was last recorded.
"Bad weather and inaccessibility has so far prevented any of it being recovered but we are confident that some will be," he said.
He moved a condolence motion in the House of Representatives and offered parliament's "severe condolence for the families and loved ones of the six Australians and the other passengers and crew who are presumed to have died".
"We mourn all those 239 passengers and crew," he said adding "We especially mourn the six Australian citizens and the one Australian resident who must be presumed dead and we grieve with their families and loved ones".
He said four Australian families had "an ache in their heart" and "nothing we can say or do can take that ache away".
"Still, the knowledge that this nation, through this parliament, has paused to acknowledge that loss, may be of some comfort in facing this terrible bereavement," he said.
Abbott said that 12 aircraft and two ships were still looking for any debris in the southern Indian Ocean.
He said black box recovery equipment was also on its way to Australia and was expected to be deployed to the search area by an Australian navy ship.
Abbott said he had pledged to Malaysian Prime Minister Najib Razak, Australia's ongoing assistance to the investigation, which has struggled over days of bad weather.
"The crash zone is about as close to nowhere as it's possible to be but it's closer to Australia than anywhere else," he said.
Six countries are now assisting in the search - Australia, New Zealand, the US, Japan, China and South Korea.
Expert analysis of a handful of faint signals sent from the plane to an Inmarsat satellite have led officials to conclude that the plane crashed in a remote part of the southern Indian Ocean.
Aircraft and ships from over 20 nations have been hunting for the Boeing 777-200 since it disappeared on March 8.
The Beijing-bound jet was carrying 239 people, including five Indians, an Indo-Canadian and 154 Chinese nationals, when it went missing an hour after taking off from Kuala Lumpur.


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