A bomb scare forced the evacuation of the Catholic pilgrimage site in Lourdes, France, late last night as 30,000 worshippers celebrated the Feast of the Assumption.

A caller to the local police station said four bombs would go off around 3pm (1am NZT).

A Lourdes spokesman said the evacuation was proceeding calmly.

On August 15, Catholics celebrate Mary's ascent to heaven, and Lourdes - where they believe she appeared 152 years ago - is a popular site to mark the event.