Paris - French authorities said on Thursday that a man with links to radical Islam had been detained in southern France suspected of plotting possible attacks on American and Russian tourists and police.
The arrest came amid renewed fears about Islamic State threats to France.
A judicial official said that the man, detained in the medieval city of Carcassonne on Monday, was suspected of terrorism links and he was being questioned. He said the man told investigators he wanted to attack tourists and later police.
A French security official called it a routine matter as police and intelligence services seek to avert a repeat of deadly Islamic State attacks on France last year.
The incident came the same day an extremist claiming allegiance to ISIS stabbed two police officials to death in a Paris suburb.
Hundreds of police, friends and neighbours marched silently on Thursday to honour the victims, police commander Jean-Baptiste Salvaing and his companion, police administrator Jessica Schneider.
Their faces solemn and lips closed, the crowd marched from Mantes-la-Jolie, where Schneider worked, to Magnanville, where she and Salvaing were stabbed at their home on Monday night.
Their 3-year-old son survived the attack, which rattled France's leadership as the country is on high alert for new extremist violence.
Attacker Larossi Abballa was killed in a police raid. Three people with links to Abballa are in custody and being questioned by anti-terrorism investigators.
French police have described growing fear after multiple attacks targeting security officers.