French authorities plan to close the "Jungle" camp with the first mass evacuations scheduled for Monday morning.
At least 6,500 migrants coming mainly from troubled parts of Africa and the Middle East live in the camp, many hoping for a better life in Britain, a few miles away across the Channel.
A group began to throw stones at the police on Sunday 1,250 of whom have been drafted in to secure the evacuation.
Police moved in with tear gas as a series of portable toilets were burnt.
Some 150 to 200 militants from the anti-globalisation "No Borders" group are also known to be present in the area.
SA - 12