At least 10 migrants are thought to be dead after a boat carrying them capsized while trying to cross the English Channel, a French coastguard spokesman has said.

A major operation is underway to rescue more than 50 people - with earlier coastguard reports putting the number of those in a "critical condition" at more than 10.

Emergency services were deployed at approximately 11.30am local time after the vessel flipped off the coast of Le Portel, on the outskirts of Boulogne-sur-Mer on France's north coast.

Those on board are understood to have entered the water in the Channel after it got into difficulty off Cap Gris-Nez, to the north of Le Portel, earlier this morning.

The hoverport in Le Portel has been shut off by the town's mayor

Local media reported that "several people" had suffered a cardiac arrest as a result of the incident, while harbours and beaches nearby have been locked down as emergency services flocked to the scene.

While the mayor of Le Portel, Olivier Barbarin, has shut beaches at the town's hoverport to allow emergency helicopters to land nearby.

France's Interior Minister, Gerald Darmanin, is set to be making an appearance on the site later this afternoon, according to French broadcaster CNews.