Clashes broke out between French riot police and migrants on Monday as authorities began destroying makeshift shelters in the grim shantytown on the edge of Calais known as the "Jungle".
Police lobbed tear gas cannisters at migrants who protested as around 20 workers moved in to start pulling down the shacks by hand under blue skies as an icy wind blew. Two bulldozers stood by but were not used.
Migrants and members of the British "No Borders" activist group, who launched projectiles at the police, also set fire to about 20 of the shelters, according to an AFP photographer and running clashes continued late into the afternoon.
Three members of "No Borders" and one migrant were arrested, according to local government officials.
The demolition of the southern half of the camp began after a court petition by charities to stop it was rejected last week.
"It's infinitely sad to see the waste of so much work that we've done in the past months," said Maya Konforti of the Auberge des Migrants (Migrants' Hostel) charity.
Volunteers and aid workers have spent months trying to improve conditions in the camp, built on a former toxic waste dump on the outskirts of Calais.
Local authorities, who have promised that no one will be evacuated by force, say 3,700 people live in the camp, and that between 800 and 1,000 will be affected by the eviction.
But charities say a recent census they conducted counted at least 3,450 people in the southern part alone, including 300 unaccompanied children.
The evicted migrants have been offered heated accommodation in refitted containers set up next door to the camp, but many are reluctant to move there because they lack communal spaces and movement is restricted.
They have also been offered places in some 100 reception centres dotted around France. However the migrants do not want to give up their hopes of Britain, which they try to reach daily by sneaking aboard lorries and ferries crossing the Channel.