The attack submarine La Perle (The Pearl), one of six in France's arsenal, had no nuclear fuel nor weapons on board, said the Mediterranean maritime authority. Some 40 people were evacuated from the vessel with no injuries reported.

The fire broke out at about 10:30 am in a hard-to-access part of the lower bow section of the submarine, and was still raging by mid-afternoon, according to the navy, which feared substantial material damage.

Navy and civilian firefighters have been deployed, and Defence Minister Florence Parly would visit the scene "as soon as conditions allow", said the ministry.

The submarine, which entered service in 1993, docked at Toulon in January for 18 months of renovation work.

The vessel, which can dive to 300 metres (984 feet) with a crew of 70, is an attack submarine used for tracking ships, escorting aircraft carriers, carrying out coastal intelligence missions, and deploying special forces.

In addition to its six nuclear-powered attack submarines, France also operates four nuclear ballistic missile submarines.

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