Police in the French port of Calais have moved in to clear makeshift camps occupied by migrants - mostly from Africa and the Middle East - who are trying to get to Britain.
The AFP news agency reported that police blocked road and sea access to the port after they obtained a court order for the camps to be disbanded.
Officials say they acted because of concerns over poor sanitary conditions.
In May 800 migrants occupying camps near the port were removed.
Calais aid workers at the scene of Wednesday's raid said that many migrants managed to escape from the police but others were arrested and driven off in buses.
A senior government official for the region told AFP that about 320 migrants were taken away. Each would be questioned and each case would be judged individually, he said.
The migrants are believed to have been taken to a secure immigrant detention centre outside Calais, where they will be given the option of either claiming asylum in France or being deported home.
A 25-year-old volunteer at the food distribution centre told AFP that the police operation began early on Wednesday morning when all camp exits were blocked and tear gas was used to stop people from fleeing.
Most people at the camps believe the UK will be a more welcoming place if they can get there.
In 2002 the French government closed the main Red Cross centre at Sangatte near Calais, but insanitary illegal camps sprung up in its place.
The migrants have been sheltering under plastic bags and sheets, without water, power or even enough food.
Some managers of welfare groups that were distributing food were also detained, charity workers said.
Police have been striving for years to disband migrant camps in and around Calais.
There are estimated to be around 1,000 refugees living on the northern French coast, with around 650 near Calais.