At least 12 people have died after a boat carrying migrants capsized in the English Channel on its way to Britain, French interior minister Gérald Darmanin said on Tuesday in a post on X, adding that two other people were still missing.

Dozens of people plunged into the treacherous waters of the busy 33-kilometre channel, which separates England from France, when the boat began sinking, according to authorities.

"Unfortunately, the bottom of the boat ripped open," said Olivier Barbarin, mayor of Le Portel near the fishing port of Boulogne-sur-Mer, where a first aid post was set up to treat victims. "It's a big drama."

A maritime rescue official who spoke on condition of anonymity because he was not authorised to discuss details of the operation confirmed that at least 13 migrants were dead.

Etienne Baggio, a spokesman for the French maritime prefecture that oversees that stretch of sea, said "more than 10" people were dead but he didn't have an exact number. The prefecture said the boat got into difficulty off Gris-Nez point.

Both Baggio and the mayor said rescuers recovered 61 people from the waters.

Sea temperatures off northern France were around 20 degrees Celsius, or about 68 Fahrenheit.

At least 30 migrants have died or gone missing while trying to cross to the UK this year, according to the International Organization for Migration.

At least 2,109 migrants have tried to cross the English Channel on small boats in the past seven days, according to UK Home Office data updated on Tuesday. The data includes people found in the channel or on arrival.

Europe's increasingly strict asylum rules, growing xenophobia and hostile treatment of migrants have been pushing them north.

British interior minister Yvette Cooper called the death of the migrants a "horrifying and deeply tragic incident" and said the work to dismantle "dangerous and criminal smuggler gangs and to strengthen border security is ... vital and must proceed apace".

The English Channel is one of the world's busiest shipping lanes and currents are strong, making the crossing on small boats dangerous. In August, two people were found dead after a boat carrying migrants trying to make the journey ran into difficulties.

"Every political leader, on both sides of our Channel, needs to be asked how many lives will be lost before they end these avoidable tragedies?" Steve Smith, CEO of the Care4Calais NGO said.

"Their continued obsession, and investment, in security measures is not reducing crossings, it is simply pushing people to take ever increasing risks to do so."

AP/Reuters