Riot police have fired tear gas at refugees in the camp in Calais as workers started demolition of migrants' shelters.
A heavy police presence has been deployed at the site after it was reported stones were thrown at some workers as they tore down temporary buildings and structures.
Some tents were even set on fire in protest at the work to clear the area.
Bulldozers moved on to the site following a ruling by a judge last Thursday that part of the Jungle can be razed to the ground.
Aid workers said police arrived at the camp at dawn and told migrants to leave the area or they faced being arrested.
French authorities have been condemned for the so-called heavy-handed response after it emerged water cannon had also been sent to the site.
Tanya Freedman, of Help Refugees, said: "We're very disappointed because the French interior minister Bernard Cazeneuve insisted in a public statement that the clearance would be done in a humane fashion.
"On the first major day of dismantling, this is the way they are going about things."
Regional Prefect Fabienne Buccio said the police presence was needed because "extremists" could try to intimidate migrants into turning down housing offers or buses to reception centres.
Authorities in France say up to 1,000 people are being removed from the camp but charities and aid groups have warned the figure is more than 3,000.
On Thursday a judge upheld a government order to evict migrants living in the southern part of the camp, although a few makeshift buildings of social importance such as a school and a theatre are to remain untouched.
Authorities have offered to relocate migrants into heated containers installed nearby, or at centers around France where they can decide whether to apply for asylum.
