PARIS: At least 27 migrants died after their dinghy capsized on Wednesday while trying to cross the Channel from France to Britain, a local mayor said.

According to fishermen, more migrants left France's northern shores than usual to take advantage of calm sea conditions, although the water was bitterly cold. One fisherman called the rescue services after seeing an empty dinghy and people floating motionless nearby.

Calais mayor Natacha Bouchart told BFM television the death toll now stood at 27, minutes after another mayor put the tally at 24.

The local coast guard said they could not yet confirm the number of deaths, adding that rescue services had found around 20 people in the water of whom only two were conscious.

They estimated that there had been about 30 people on the dinghy before it capsized.

French Interior Minister Gerald Darmanin said he was heading for the coast. "Strong emotion in the face of the tragedy of numerous deaths due to the capsizing of a migrant boat in the English Channel," he wrote in a tweet.

Two helicopters and three police or rescue boats were at the scene, local authorities said.