Riot police fired tear gas to push back migrants who set fire to tents and threw stones as bulldozers and demolition teams moved into the Calais "Jungle" camp yesterday.
The clashes came as officials attempted to remove migrants from their shacks after a judge upheld a decision to evict them from the southern part of the squalid camp.
Around 150 to 200 migrants and activists threw stones at police, who later deployed a water cannon.
A British woman who is a member of the No Borders activist group, which French officials have accused of encouraging migrants to attack police in the area, was arrested as the operation began, police said.
Helmeted workers in orange overalls pulled down makeshift structures where migrants had been sleeping in the muddy, rat-infested settlement of wooden shacks and tents that is home to several thousand people.
Police arrived at the camp at dawn and told migrants in the southern section that they had to move out or they would be arrested, aid workers in the camp said.
"That was my home," said one man, a 17-year-old Afghan who gave his name as Salahudin, sitting beside the smouldering, smoking remains of a shack. He said his tent had been set ablaze when a police tear gas grenade fell on it. Other migrants had set fire to their makeshift homes in protest at the eviction.
Police arrived at the camp at dawn and told migrants in the southern section that they had to move out or they would be arrested, aid workers in the camp said.
Lines of police vans gathered on the perimeter of the slum as migrants and refugees were told their only option now was to move.
The operation is the most dramatic step France has taken to end Calais'
migrant problem, which has festered for years, bolstering support for the far-Right and causing tension with Britain.
The French government said the removal of up to 1,000 migrants intent on reaching Britain was a "humanitarian operation" and that they are being offered accommodation in containers recently installed nearby or in migrant centres elsewhere in the country.
But many migrants, most of whom have fled war, poverty or persecution in the Middle East or Africa, are reluctant to move because to be allowed access to the containers, they have to be fingerprinted. NGOs also say there are more than 1,000 migrants in the southern section of the camp and that many will be left with nowhere to go.
Yesterday's operation came after a judge in the city of Lille ruled last Thursday that a partial clearance should go ahead, but that schools, places of worship and other common spaces in the sector should be left intact.
The migrants have grown increasingly desperate since border controls in Calais were reinforced by the British border force and French police since the summer. Britain has provided security fencing to prevent migrants from storming the ferry port, the entrance to the Channel Tunnel or the Eurostar rail tracks.
Belgium has reintroduced border controls to prevent migrants from the "Jungle" trying their luck from Zeebrugge and other Belgian ports.
The demolition of the Jungle comes before talks on Thursday between French president Francois Hollande and David Cameron. Britain has put substantial pressure on France to stem the flow of migrants getting across the Channel, and has funded a huge increase in security measures around the port and tunnel in Calais.
