French riot police have evacuated at least 150 Afghan boys and men from the "jungle", a makeshift migrant camp on the Channel coast.

Riot police took up positions at dawn outside the tent city on a patch of sandy scrubland in Calais as the remaining migrants gathered behind banners with slogans pleading with the French authorities for shelter and protection.

As the first dozen officers entered the camp a small group of rights activists formed a human chain trying to bar access to the migrants, shouting "no border, no nation, stop deportation".

Police led out the migrants one by one who followed without resistance amid the angry shouts of the protesters and with dozens of journalists looking on.

Thousands of mainly male migrants, from Afghanistan, Iraq and other troubled nations, have headed to Calais in the past decade to try to jump on a ferry or a train crossing the Channel tunnel to Britain.

But government officials say the Calais "jungle" has become a haven for people-smuggling gangs and a no-go zone for locals, with appalling sanitary conditions blamed for an outbreak of scabies in the past few months.

From a peak of 700 mostly Afghan Pashtuns based in the "jungle" in June, aid groups say two thirds have fled since the government indicated it would close the camp in April.

Aid groups also say the crackdown will simply push migrants further underground, making them more vulnerable to traffickers and criminal gangs.

- AFP