A major search and rescue operation is underway in the English Channel, where a boat with about 50 migrants overturned a while ago, off the French coast of Boulogne-sur-Mer.

At least 10 people were rescued and are in critical condition, a spokesman for the French coast guard said. The rescued were pulled from the water with cardiopulmonary arrest.

At least 10 other migrants died, according to La Voix du Nord newspaper.

In a sign of the seriousness of the situation, CNews TV reported that outgoing French Interior Minister Gérald Darmanen was expected to be at the site where rescue operations were underway.

Tackling illegal immigration is a priority for both the British and French governments.

More than 2,000 people have arrived in Britain on small boats in the past seven days, according to British government figures.