Families whose relatives disappeared aboard Malaysia Airlines Flight MH370 last year vented their frustration at conflicting signals from Malaysia and France over whether the finding of a plane part had been confirmed.

Malaysia's prime minister announced that a plane wing section that washed up on the French island of Reunion in the Indian Ocean was "conclusively confirmed" to be from Flight 370.

He said he hoped the news would end "unspeakable" uncertainty for relatives of the 239 people aboard, and the announcement was in line with the Malaysian conclusion that the plane crashed in the Indian Ocean, killing all aboard.

But French officials with custody of the wing part said only that there were strong indications the barnacle-encrusted part - known as a "flaperon" - was from the flight and that they would work further to try to confirm the finding today.

"Why the hell do you have one confirm and one not?" asked Christchurch, New Zealand, resident Sara Weeks, whose brother Paul Weeks was aboard the flight, which disappeared on March 8 2014, while en route from Kuala Lumpur to Beijing.

"Why not wait and get everybody on the same page so the families don't need to go through this turmoil?

"After 17 months, we need definite answers. We need to progress, get answers, move toward further answers, and get some closure along the line."

About two-thirds of the passengers were from China, and Xu Jinghong said she could not understand why Malaysian and French authorities did not make their announcement together.

"I am very angry - so angry that my hands and feet are cold," said Ms Xu in central Beijing.

"The announcement was made without experts from France present. I don't understand how the procedure can be like this."

The announcement by Malaysian prime minister Najib Razak appeared to give the first strong physical evidence of a crash.

That could put to rest several theories that many relatives have refused to rule out, including that the plane and its passengers were hijacked and intact in some still-secret location.

However, any potential certainty was diluted by the word from Paris, where deputy prosecutor Serge Mackowiak said the "very strong conjectures" that the wing part was from Flight 370 still needed to be "confirmed by complementary analysis".

It was unclear whether the mix-up was a result of miscommunication between the two countries, or whether Malaysian officials were overeager to send out some definitive signal for relatives of the missing.

In any case, a full confirmation of the wing part was not likely to bring total closure for relatives, with the rest of the plane and the bodies still missing.

Jiang Hui, whose mother was on board, said there was still a lack of evidence to prove that the plane crashed as was announced by Malaysian officials last year.

At the time, they cited thorough analysis of the relatively limited satellite data available for the flight. Major questions still remain, including why the plane went off course, crossed back over Malaysia and went south into the Indian Ocean.

"The finding of debris does not mean the finding of our next of kin," Mr Jiang said.

In Kuala Lumpur, Melanie Antonio - whose husband was a flight attendant on Flight 370 - said she was not sure what to feel.

"I'm numb, I'm not sad," she said. "It's just a flaperon, it doesn't prove anything. We still need the wreckage to prove. I just want anything that can tell me my hubby is gone."

Jacquita Gomes, also the wife of a flight attendant, echoed that sentiment: "If it's not too much to ask, I still want the remains of my husband."

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