The device, found at a building site in the northwestern port city of Saint-Nazaire, was  dismantled by 1600 GMT, the local government said in a tweet.

"The destruction of the detonator resulted in a small explosion," said the Loire-Atlantique prefecture, adding that the procedure had gone as planned.

The 130-centimetre (4-feet) bomb, dropped by the British air force, was in an urban area, so the team said they had to clear everyone within 400 metres.

Around 2,300 residents were evacuated as the experts dug a hole around the bomb before cutting it up and taking it away to be destroyed.

Saint-Nazaire was a vital port during World War II, providing the occupying Nazi forces with a dock for their warships in the Atlantic.

The British bombarded the port in 1942, putting it out of action for the rest of the war.