Dozens of people are feared to have died while trying to cross the English Channel to the UK, according to French media reports.
The Press Association reports that a fishing boat sounded the alarm earlier on Wednesday after spotting several people at sea off the coast of France.
The French AFP news agency has reported that "more than 20" people have died.
French interior minister Gerald Darmanin confirmed on Twitter that people had died but did not give a number.
And French prime minister Jean Castex said the shipwreck was a "tragedy".
"My thoughts are with the many missing and injured, victims of criminal smugglers who exploit their distress and injury," he said.
A rescue operation is underway in the Channel by air and sea as French and British authorities search for anyone still in the water.
Three French vessels were close to each other in the middle of the Channel off Calais on Wednesday afternoon, according to the vesselfinder app.
A number of people are also believed to have reached Britain in small boats on Wednesday, with people seen being brought ashore in Dover by immigration officials.
Dover MP Natalie Elphicke said: "This is an absolute tragedy. It underlines why saving lives at sea starts by stopping the boats entering the water in the first place.
"As winter is approaching the seas will get rougher, the water colder, the risk of even more lives tragically being lost greater.
"That's why stopping these dangerous crossings is the humanitarian and right thing to do."
The Dover Strait is the busiest shipping lane in the world and has claimed many lives of people trying to cross to Britain in inflatable dinghies.
More than 25,700 people have made the dangerous journey to the UK in small boats this year - three times the total for the whole of 2020, according to data compiled by the PA news agency
