Kuala Lumpur: Malaysia Airlines has described confirmation that a barnacled-encrusted wing part that washed up on the remote Indian Ocean island of Reunion was from MH370 as a "major breakthrough" in solving one of aviation's greatest mysteries.

"We expect and hope that there would be more objects to be found which will be able to resolve this mystery," the company said in a statement.

Malaysia's Prime Minister Najib Razak also described the finding of the wing part as a breakthrough.

"Today, 515 days since the plane disappeared, it is with a heavy heart that I must tell you that an international team of experts have conclusively confirmed that the aircraft debris found on Reunion Island is indeed from MH370," Mr Najib said in a televised statement, at a press conference called at 2am Kuala Lumpur time on Thursday.

However, France stopped short of declaring it was certain the part was from MH370, saying that there was only a "very strong presumption" that it was the case.

Mr Najib's statement suggests MH370 flew off course for hours early on March 8 last year but it is not known if the passengers were then alive or already dead. Six Australians were on board.

"The burden and uncertainty faced by the families during this time has been unspeakable," Mr Najib said.

"It is my hope that this confirmation, however tragic and painful, will at least bring certainty to the families and loved ones of the 239 people on board MH370 … they have our deepest sympathy and prayers."

The comments by Malaysia Airlines and the Malaysian leader appear to reflect the opinion of experts that more debris will be found despite winds and sea currents pushing the wing part almost 4000 kilometres from where the plane is believed to have crashed.

They also reflect confirmation that an Australian-led search is being conducted in the right area of the southern Indian Ocean.

Mr Najib said the search area is a "remote, inhospitable and dangerous area and, on behalf of Malaysia, I would like to thank the many nations, organisations and individuals who have participated in the search".

Mr Najib called the press conference in the middle of the night. Only Malaysian-accredited journalists were permitted to attend.

A spokesman for Australian Transport Minister Warren Truss said the government noted the statements from France and Malaysia and was planning its own briefing.

Mr Najib is engulfed in a political corruption storm over allegations surrounding a state investment fund that he heads. The allegations that involve how almost $1 billion was deposited into his personal account threaten his position as prime minister.

Mr Najib denies any wrongdoing. Throughout the MH370 search, Mr Najib has insisted on personally making major announcements.

French statement

France's statement on the debris underscored the strong chance of the plane's part belonging to flight MH370.

Paris prosecutor Serge Mackowiak said this was based on technical data supplied by both the manufacturer and airline but gave no indication that experts had discovered a serial number or unique markings that would put the link beyond doubt.

Boeing representatives confirmed that the flaperon came from a 777 jet "due to its technical characteristics, mentioning the colour, the structure of the joints", he said.

Malaysia Airlines was able to provide documentation of the actual aircraft used on flight MH370.

"On this basis, it was possible for a connection to be made between the object examined by the experts and the flaperon of the Boeing 777 of MH370," Mr Mackowiak told reporters in Paris.

The wing part bearing the number BB670 was sent to offices of France's BEA crash investigation agency in Toulouse, which verified it was indeed the first trace of the lost plane to be found.

Investigators in France ascertained that the debris, a 2-2½ metre wing surface known as a flaperon, belonged to MH370 just days after Malaysia identified it as being part of the same model as MH370, a Boeing 777.

The latest statements bring some closure to the relatives of those on board but shed no light on what happened to the airliner.

Family anger

However, like at the time of the plane went missing in March 2014, families were angered to learn the latest news through the media rather than through direct contact from the governments or Malaysia Airlines.

A preliminary report on the investigation this year found there was no evidence to suggest any motive for hijacking the plane by either of two pilots or the crew.

Wild theories have swirled around the mystery as many of the relatives of families clung to the hope their loved ones were still alive.

"I would like to assure all those affected by this tragedy that the government of Malaysia is committed to do everything within our means to find out the truth of what happened," Mr Najib said.

The plane piece washed up on Wednesday last week on Reunion, a volcanic island of 850,000 people that is a full part of France, located in the Indian Ocean near Madagascar.

The discovery of the flaperon led to a frantic search for more possible wreckage from the missing plane on the island.

But no further wreckage is believed to have been found.

Mr Najib said the MH370 disappearance marked Malaysia as a nation.

A Malaysian aviation expert Harridon Mohamad Suffian, of the Universiti of Kuala Lumpur, said while more wreckage could be expected to be washed up it was impossible for the entire wreckage of the plane to be swept to land.

"The whole wreckage would be submerged in the ocean," Dr Harridon said.

"Only some parts - debris such as the flaperon and flap and other objects with high buoyancy torn from the plane would be washed ashore," he said.

Tony Abbott responds

Deputy Prime Minister Warren Truss said Australia respected the Malaysian government's confirmation but acknowledged there remained "a very small element of doubt" the wreckage was not from MH370.

The barnacles on and paint samples from the wreckage were being examined for details such as its time in the water and its repair history that "might prove beyond any doubt" it was part of the missing plane.

He said the wreckage had been in the water for "too long" for experts to use it to target exactly where it came apart from the aircraft and how it floated in that direction.

Prime Minister Tony Abbott told Melbourne radio 3AW that the search, which has cost $100 million so far, would continue.

"We'll continue the search," he told host Neil Mitchell.

"We owe it to the families of the people lost on that plane to try to solve the mystery.

"We owe it to the travelling public who obviously want to be confident of their safety in the air.

"Let's hope we can turn something up," he said.

<a data-cke-saved-href="/interactive/2015/mh370-map/" <span class="scayt-misspell-word" data-scayt-word="href">href</span>="/interactive/2015/mh370-map/">Possible debris located for MH370</a>

with Reuters