UPDATED

An aircraft wing fragment washed ashore on the Indian Ocean island of Reunion came from Malaysia Airlines Flight 370, which disappeared more than a year ago with 239 people aboard, experts say.

Malaysia's prime minister Najib Razak said on Wednesday that "an international team of experts have conclusively confirmed that the aircraft debris found on Reunion Island is indeed MH370".

Malaysia's Prime Minister Najib Razak confirms the debris found on Reunion Island is from missing Malaysia Airlines flight MH370 in Kuala Lumpur. Photo: Olivia Harris, Reuters

The barnacle-encrusted wing fragment was sent to France, where experts began examining it on Wednesday. Investigators will analyse the metal with high-powered microscopes to probe what caused the plane to go down.

The Boeing 777 disappeared after veering far off its planned northerly course from Kuala Lumpur in Malaysia to Beijing.

The first ever physical evidence of the aircraft was found on the French territory of Reunion Island, thousands of miles from the site near Australia where the plane is believed to have gone down.

"We now have physical evidence that, as I announced on 24th March last year, flight MH370 tragically ended in the southern Indian Ocean," Mr Najib said in Kuala Lumpur.

"The burden and uncertainty faced by the families during this time has been unspeakable. 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 onboard MH370. They have our deepest sympathy and prayers," he said.

In a statement, Malaysia Airlines said the flaperon, part of the plane's wing, found on Reunion Island on July 29 was confirmed to be of Flight 370 by the French agency that investigates air crashes, known as the BEA, the Malaysian investigation team, a technical representative from PRC and the Australian Transportation Safety Bureau in Toulouse, France.

"Family members of passengers and crew have already been informed and we extend our deepest sympathies to those affected," it said.

The statement said this "is indeed a major breakthrough for us in resolving the disappearance of MH370. We expect and hope that there would be more objects to be found which would be able to help resolve this mystery."