At least 27 people died after an inflatable boat packed with people fleeing conflict in the Middle East and North Africa sank, authorities said.
One passenger was pulled from the water alive, a fire brigade spokeswoman told French television.
Officials did not specify what countries the victims were from, but said many had arrived by boat in the southwest of France, from Libya, where they were trying to cross the Mediterranean Sea and seek asylum.
Police on the French Mediterranean island of Corsica said the boat, which was about 150 yards off a beach near the city of Bastia, may have run into trouble on Thursday as it was trying to approach the island.
“Fishermen saw a boat that had capsized, with many people floating in the water,” police chief Stephane Dalmer told France 2 television. “There were many bodies.”
France has seen a sharp increase in the number of people illegally trying to cross the Mediterranean from Libya as the war-torn country has descended into chaos and criminals control parts of the Mediterranean Sea.
The European Union has been reluctant to provide military or economic support to combat the smuggling networks, which send heavily armed traffickers armed with rocket-propelled grenades and Kalashnikov rifles.
More than one million people reached the EU seeking asylum last year. Most are from the Middle East and North Africa, where civil war, poverty and persecution have fueled the movements.
Most arrive in Europe through Italy, which faces the heaviest burden.
Prime Minister Philippe Montebourg said this month that the Europe Commission should be abolished and that the EU budget should be shared out with countries sharing some of the burden of refugees.
The European Commission was not immediately available for comment.
On Thursday night, a boat heading for Europe, carrying up to 50 people, rammed a motorboat packed with fishing workers at another beach in Corsica. One person was killed and one injured. No other details were available.
On Wednesday, 34 migrants drowned when their boat capsized in the sea off the coast of northern Africa. Five members of a family, all Moroccan, have been taken into custody, said a spokesman for Malta’s defense ministry.