French police have detained 190 people in an operation against undocumented migrants near the port of Calais, officials say.
More than 300 officers were involved in the operation on Tuesday morning, regional state authorities said.
The port has become a magnet for migrants trying to enter the UK illegally across the English Channel.
There are estimated to be about 1,000 migrants living in makeshift camps around Calais.
Police cordoned off a migrant squatter camp known as "the jungle" and detained 150 people in an early morning raid. Forty other migrants were detained at two other locations along the coast, officials said.
Police said they had planned the operation for some time and all the arrests were made peacefully.
The police operation came two days before Immigration Minister Eric Besson was due to visit Calais for talks on the migrant situation, a state spokeswoman said.
"It is an attempt to dismantle people-trafficking networks," she said. "It is an operation to destabilise the networks and try to find the smugglers."
Charities are donating food and clothing to the migrants
She added that many of the those arrested said they were from Afghanistan. They were taken into custody in Calais, Boulogne and Lille.
The French and British governments are currently discussing the creation of a new immigrant holding centre within the British-controlled zone of the Calais docks.
The BBC's Emma Jane Kirby, in Paris, says this would allow London and Paris to break through the quagmire of asylum law and to send illegal immigrants home more easily.
A refugee centre at Sangatte, near Calais, was closed in 2002 and bulldozed, under pressure from Britain.
Migrants who have since set up squatter camps around the port receive no help from French authorities, but charities have stepped in with donations of food and clothing.
Another BBC correspondent, Andrew Bomford, who recently visited the camps, said migrants had alleged that the hard-line French riot police, the CRS, had thrown tear gas into their camps, and frequently arrested and harassed them.
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