The French interior ministry has sent in extra police to boost security at the Channel Tunnel entrance in Calais after over 100 migrants got a third of the way through the tunnel to Britain and disrupted cross-channel traffic.
The attempt to go through the tunnel from France to Britain in the early hours of Saturday came as the daily flow of thousands of migrants and refugees flocking to Europe's shores showed little sign of easing, with 168,000 arriving in September alone, UN figures showed.
Most are seeking refuge in Germany or Sweden, but others have continued their journey to France in the hope of somehow crossing the Channel to reach England.
Eurotunnel, which operates the complex, said the incident was unprecedented, with migrants aggressively attacking its staff.
"This has never been seen before, it was a determined and well-planned attack," a spokesman told AFP of the incident, which took place shortly after midnight at the entrance to the tunnel near the northern French port city of Calais.
He said the group "ran through the terminal, pinning a number of staff members to the ground and throwing stones at them."
Traffic through the Channel Tunnel, which connects Britain and France, was halted for more than seven hours after a group of 113 migrants stormed into the tunnel.
Train journeys resumed later on Saturday but with delays of up to three hours.
The regional prosecutor's office said 23 of the migrants involved had been arrested and held in custody.
An extra 220 police, some armed, were being deployed to Calais to step up security, boosting the total presence there to around 750 officers.