French authorities began dismantling the sprawling refugee camp in Calais on Monday, taking down tarpaulin roofs and plywood walls that have been the temporary home for thousands of migrants hoping to make their way to a better life in Britain.

A flashpoint on the edge of the Channel, the camp sprang up years ago in the port city, which has both ferries and the Eurotunnel rail to Britain. But it has grown explosively in the past year amid Europe's migrant crisis, now housing about 4,000 people and fuelling far-right sentiment in both Britain and France.

One by one, helmeted workers pulled down makeshift structures where migrants sleep in the southern sector of the camp, after a court ruled that the shanties could be destroyed but not the common spaces that have also sprung up, like places of worship, schools and a library.

A cordon of police formed a perimeter around the demolition crews, to block what local authorities described as "intimidation" tactics by activists.

French authorities have offered to relocate uprooted migrants into heated containers installed last month nearby or at centres around France where they can apply for asylum. Many have resisted the move, fearing it will hurt their chances of reaching Britain, and some migrant advocates say there isn't enough space in the new area.