Police in France's northern port of Calais fired tear gas on Wednesday on migrants trying to force their way onto trucks in a desperate bid to get to Britain after they threw stones at security forces.
The incident is the latest in a series of confrontations between asylum seekers and authorities in the port, which trucks go through to board ferries bound for Britain.
The port is struggling to stem a tide of illegal migrants trying to cross the Channel to Britain, which they see as having a favourable asylum policy, despite a slew of recent measures including tighter security and policing.
Authorities in the Pas-de-Calais department where the port is located said some 250 migrants grouped together just outside the port on Wednesday morning. One of them fell while trying to get onto a truck and hurt his head.
When an ambulance arrived to take him to hospital, a big group of migrants tried to stop the vehicle from driving him away, they added.
They then tried to prise open wire fencing to get into the area where trucks are checked before they board ferries and threw stones at police, who responded with tear gas, authorities said.
By early afternoon, the situation had returned to normal.
The problem in Calais is not new, and illegal camps of migrants have sprung up in the area since French authorities closed down the infamous Sangatte immigrant detention centre in 2002.
But the crisis has spiralled, prompting the city's mayor Natacha Bouchart to threaten to shut down the port entirely in protest at London's perceived lack of action or help over the problem.
Britain has since offered to send over the strong security fences used at a recent NATO meeting in Wales.
French authorities have already arrested around 7,500 illegal immigrants trying to cross the Channel this year, and security has been ramped up.