French riot police sprayed migrants with a chemical irritant as they tried to storm the Channel Tunnel.

The group, which broke down several security fences late Saturday, was forced to retreat by riot police as the migrants attempted to breach the final fence near the entrance of the tunnel, which links France with Britain.

The migrants, estimated to number around 200 by an AP journalist, faced off for close to an hour with security forces, chanting slogans including: "Open the border" and "We are not animals."

The Channel Tunnel is a 50-kilometre rail tunnel beneath the English Channel.

Thousands of migrants have been scaling fences near the tunnel in recent weeks, hopping on freight trains or trucks destined for Britain. One man was fatally crushed by a truck.