Paris/London, Nov 25 (IANS): Thirty-one migrants died when their inflatable boat sank off Calais in northern France, the French Interior Minister Gerald Darmanin has announced.

The boat had set out to cross the Channel to the UK.

According to the International Organisation for Migration, the incident which happened on Wednesday is the biggest single loss of life in the Channel since it began collecting data in 2014.

"Around 2 p.m., a fisherman reported the discovery of about fifteen bodies floating off Calais," French radio France Info reported.

French President Emmanuel Macron ordered an "immediate reinforcement of resources for Frontex at the external boarders of the EU," Xinhua news agency reported.

France will not let the Channel become a "cemetery," Macron said.

British Prime Minister Boris Johnson tweeted: "I am shocked, appalled and deeply saddened by the loss of life at sea in the Channel. My thoughts are with the victims and their families. Now is the time for us all to step up, work together and do everything we can to stop these gangs who are getting away with murder."

Meanwhile, Darmanin arrived in Calais later in the evening, where he met with Mayor of Calais Natacha Bouchart in the hospital where the rescued migrants are being treated. He reaffirmed the criminal nature of the smugglers who organise these crossings.

The Dunkirk prosecutor's office has announced the opening of an investigation for "assistance for illegal entry in an organised group" and "aggravated manslaughter."

The British government announced in July that it will overhaul its asylum system to make it a criminal offence to knowingly arrive in the country without permission.

In a report published on November 19, the Maritime Prefecture of the Channel and the North Sea said it had recorded 31,500 attempts to leave for Britain. And 7,800 migrants had been rescued since the beginning of the year, while seven people had died or disappeared.