French President Francois Hollande says that authorities have received 9,000 tips related to Islamic extremism through a dedicated hotline and a website.

France officials believe some 600 Muslims have left the country for Syria and Iraq, but the thousands of tips offer a hint of the scale of the concern over religious radicalism in France.

Hollande was quick to note that not all the tips were linked to genuine problems.

The figure was given during a televised exchange with Veronique Roy, whose son is believed to have died in Syria after converting to a radical form of Islam.

Roy was one of four citizen panelists brought as part of a town hall-style question-and-answer session at Paris' Museum of Man on Thursday evening.