PARIS (REUTERS) - Students at five Paris high schools returned to class on Tuesday after thousands of them had to be evacuated following bomb threats in anonymous phone calls, the Paris education authority said.

Police intervened at the Henri IV, Louis Le Grand, Fenelon, Condorcet, Montaigne and Charlemagne schools, all prestigious schools in up-market areas, after five of them received bomb threats around mid-morning, the Paris education authority said.

Students were confined to the schoolyards and safe places for several hours while bomb squads and police dogs inspected the premises.

No devices have been found so far.

"It's probably just a malicious caller," an official at the Louis Le Grand lycee told Reuters.

Checks were still being made in one school, but class had resumed in all other academies by mid-afternoon, a spokeswoman at the Paris education board said.

France has been on high alert since militant Islamist gunmen and suicide bombers killed 130 people in and around Paris on Nov 13.