Six people died after a boat carrying migrants sank in the English Channel, authorities say.

French officials said the country's navy rescued 42 people and are transporting them to Calais, including five of the people who lost their lives. British ships rescued around 13 people, who have been taken to Dover in the UK.

Local mayor Franck Dhersin tweeted an image of some of the migrants who had been rescued aboard a rescue boat covered with gold aluminum blankets.

"Here is another catastrophe off the coast of Calais/Wissant with several drowned migrants. One day, we will have to stop simply recording the number of deaths in the Channel and the Mediterranean," he posted on X, formerly known as Twitter.

The English Channel is one of the world's busiest waterways and crossing on small boats is extremely dangerous.

Human traffickers typically overload vessels and deaths are common in the choppy seas.

UK Prime Minister Rishi Sunak -- whose governing Conservatives have been struggling in the polls -- made stopping boats making the perilous crossing across the English Channel one of his top priorities.

But 755 migrants were detected crossing the channel to the UK Thursday, government figures showed. The figure is the highest recorded in a single day this year.

As of this week 100,000 migrants have crossed the Channel since 2018, including nearly 16,000 this year, figures show.

On Friday 39 asylum seekers were removed from a controversial barge meant to house hundreds of people after Legionella bacteria was discovered in the water.

French authorities have stepped up patrols and other deterrent measures after the UK agreed in March to send Paris hundreds of millions of euros annually.

French Prime Minister Elisabeth Borne said in a tweet that her "thoughts are with the victims" of the migrant boat that capsized.

"I salute the commitment of the rescue teams mobilized around the (French Navy) who saved around fifty shipwrecked people," she said in the post on X, formerly known as Twitter, adding that French secretary of state for the sea, Herve Berville, is heading to the scene.

UK Home Secretary Suella Braverman also tweeted, writing, "My thoughts and prayers are with those affected by the tragic loss of life in the Channel today."

"This morning I spoke with our Border Force teams who have been supporting the French authorities in response to this incident," she added.