PARIS (AP) - French President Francois Hollande is warning of threats to France related to fighting in Mali and Syria, but says there is "no reason to raise the vigilance level higher."

France has been on increased alert for terrorist attacks since January, when the French military moved into Mali to fight Al Qaeda-linked extremists.

Mr Hollande went to Paris' Charles de Gaulle airport on Thursday to review security measures and meet security officials. He said the check was related to "threats that concern France in particular" tied to Mali and France's support of Syrian opposition fighters, not to the Boston bombings.

A French official, speaking on condition of anonymity to discuss sensitive security matters, said there had been contacts with US security officials but no European leads related to the Boston attacks have emerged.