Fires cut through a swath of the Calais "Jungle" on Wednesday, sending migrants fleeing as French authorities prepared to ramp up demolition of the notorious camp.

The blazes spread just hours after workers protected by police moved in on Tuesday to clear the squalid camp that has been home to an estimated 6,000 to 8,000 migrants, many with hopes of reaching the United Kingdom.

"Our tents were burning. Someone set fire to them, though I don't know who," said Siddiq, a 16-year-old boy, who was forced by the flames to sleep under a bridge at the camp's entrance.