A 22-year-old radicalised convert to Islam has been arrested in France on suspicion he was planning to attack American and Russian tourists, legal sources said on Thursday.

The suspect had gone to the southern city of Carcassone "with a view to carrying out a violent act, in particular targeting Americans and Russians," a judicial source said.

He was arrested on Monday night and had in his possession "a knife and a small mallet", the source said.

The suspect comes from the southern French town of Lunel -- notorious for the number of residents who have left to wage jihad in Syria -- but has been living in the nearby Tarn region.

A source close to the investigation also confirmed the man was suspected of planning an attack on tourists.

A medieval walled city and UNESCO World Heritage site, Carcassone is one of France's biggest tourist attractions with its drawbridges, watchtowers and cobbled streets.

Source: AFP