A local government source told AFP that aside from the sprawling "New Jungle" where some 3,000 people have set up camp -- most seeking desperately to get to England -- "any illegal settlement cannot remain and will result in evacuation."
With nowhere to go, about 50 of those evacuated staged a sit-in at the port, accompanied by members of the "No Border" movement, refusing to go to the "New Jungle."
The slum-like migrant camp sprung up after the closure of notorious Red Cross camp Sangatte in 2002, which had become overcrowded and prone to violent riots.
That camp also strained cross-Channel relations as London saw it as luring migrants to Calais from where they tried to make their way to England.
However migrants and refugees have kept coming and the "New Jungle" has swelled along with the numbers of those making often deadly attempts to smuggle themselves across the Channel.
"The Syrians refuse to go there because of the insecurity there," said an official from Medecins du Monde (Doctors of the World).
Police fired tear gas and took three "No Border" militants into custody while driving the group out of their makeshift camp.
Two other camps where Syrians and African migrants have been living for several months, were also dismantled.
Another, home to mostly Eritreans, was bulldozed.
Under the driving rain, groups of people, including women and children, wandered around Calais looking for a new place to set up home.
The move comes after France was criticised for offering aid and lodging to new refugees arriving in Germany, while abandoning the thousands of "migrants" already living in France in camps like the New Jungle.
"For years we've been asking the government to do more to respond to the needs of those in Calais,” Jean-François Corty from Médecins du Monde told The Local, adding that the calls for help by his group and other charities had mostly fallen on deaf ears.
The migrants and refugees in Calais initially tried to smuggle themselves onto trucks crossing on ferries to make their way to Britain, a promised land for them, but changed tactics as security was stepped up.
In July hundreds tried to storm the Eurotunnel site nightly to enter the undersea tunnel -- several of whom paid with their lives -- but figures have fallen amid tighter security.
Calais is only a footnote in the migration crisis sweeping Europe as a flow of refugees from conflict-torn Middle Eastern nations risk their lives on a deadly journey to reach the European Union.