A French submarine that went missing in the western Mediterranean in 1968 with 52 sailors on board has been found, ending a 51-year wait for families of the crew who continue to seek answers to the naval disaster.

Key points: The submarine Minerve went missing off France's southern coast

The submarine Minerve went missing off France's southern coast The discovery brought "joy and relief" to the families of those on board

The discovery brought "joy and relief" to the families of those on board The vessel was found at a depth of 2,370 metres

The diesel-electric Minerve submarine was lost off France's southern coast on January 27, 1968.

"We found the submarine Minerve last night located 45 kilometres south of Toulon, about 20 kilometres further south than where it was searched for in 1968," French Navy Vice-Admiral Charles Henri du Che told reporters in Toulon.

Admiral Christophe Prazuck, the head of the French navy, tweeted a photo of the discovery.

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French Defence Minister Florence Parly described the discovery as "a success, a relief and a technical feat", adding she was thinking of the families who had "waited for this moment for so long."

At the start of the year, Ms Parly announced a new search mission involving naval vessels and marine experts following fresh demands from families for an effort to find the final resting place of their loved ones.

The cause of the loss of the Minerve has never been confirmed, but the news that it has been found brought joy and relief to families.

The son of the Minerve's captain, Herve Fauve, said the discovery was "hugely emotional" and came after years of calling for the search mission.

"These 52 sailors had been abandoned in some ways."

The discovery was ultimately made on Sunday by a boat belonging to private US company Ocean Infinity, which found the Minerve at a depth of 2,370 metres, a senior French naval officer said.

Ocean Infinity has also been involved in previous searches for the missing Malaysia Airlines flight MH370, which disappeared on March 8, 2014. Six Australians were among the 239 people on board.

In keeping with naval tradition, the wreck of the Minerve will be left untouched.

AFP