PARIS (Reuters) - French anti-terrorist police have arrested 10 far-right militants after an investigation showed they may have had vague plans of carrying out a violent attack on a place of worship or a person, a court official said on Tuesday.  TV station M6 said the men, aged between 17 and 25 were arrested in Seine-Saint-Denis, north of Paris, and in the Mediterranean port city of Marseille. They were suspected of planning attacks on mosques, it said. The court official, speaking to Reuters, said they may also have been targeting a person - a politician, a migrant or a drug dealer.  More than 230 people have been killed in attacks by Islamist militants in France over the past three years and the country has been under a state of emergency since late 2015, following an attack on Paris in November 2015.  