PARIS

French authorities have started on Monday morning clearing refugees’ tents, tin homes and shelters in the southern part of the "Jungle" camp in the northern port city of Calais amid great numbers of French riot police.

Several people sat on top of the rooftops of their homes to prevent their demolition, footage shared by charities working in the camp showed.

Police reportedly arrived at 7 a.m. (0600GMT) local time and surrounded the camp, telling residents they must leave within an hour or face arrest.

The move comes after Lille's administrative court validated last week the French government's decision to demolish and evacuate the southern part of the camp.

The spokesman for the Pas-de-Calais prefect's office said at the time that “the order is applicable, except for common social areas [places of worship or schools],” and that it would be “ soft”.

However several nonprofits and NGOs protested the massive police presence in an area where more than 4,000 refugees - attracted by the nearby Channel tunnel terminal and the Calais port as a route to the U.K. - have been a constant despite French attempts to disperse them.

“No volunteers access. People removed from houses. Police blocking entry. This is what they call a ‘soft demolition’,” the Good Chance Calais NGO tweeted.

“Police everywhere. This is the opposite of what the prefecture promised. Lies again. Soft demolition means hard,” it added.

French broadcaster BFM TV reported that a British activist from the group "No Borders" had been arrested at the camp.

The French government ordered the demolition of the camp saying the move aimed at reducing the population of the Jungle to 2,000 people and that it would only affect between 800 and 1,000 people who would be moved into refitted shipping containers set up nearby.

But according to Calais Migrant Solidarity, a charity working in the Calais camp, “there are still more than 5,000 undocumented people. Many more are on their way." The U.K.-based NGO Calais Action said the exact figure was 5,497, with around 3,450 people living in the southern part, including 300 unaccompanied children.

The presence of large numbers of refugees in the area has persisted since 1999 when the Red Cross Sangatte reception center became rapidly overcrowded and the “Jungle” was established in late 2014.