MILAN — Four Mediterranean Sea shipwrecks in the past 2 1/2 days have caused about 340 migrants to die or disappear, making 2016 the deadliest year on record for asylum seekers risking the dangerous voyage to Europe, a migration organization said Thursday.

The shipwreck causalities bring to over 4,500 the number of migrants who have died or disappeared crossing the Mediterranean so far this year, according to the International Organization for Migration figures. The total compares with the 3,770 people reported dead or missing last year, the previous record.

The organization said Thursday that the death toll is rising as smugglers force departures despite rough, winter seas.

”What is shocking is the cruelty,” Flavio Di Giacomo, Italy spokesman for the International Organization for Migration, said. ”The traffickers are forcing people to depart despite the prohibitive sea conditions. When they get to the beach, migrants who don’t want to go are forced to get on board, even with violence.”

Di Giacomo said traffickers care little if the migrants make it alive.

The impossibility of recovering bodies of migrants lost at sea means that humanitarian organizations must rely on the accounts of survivors to tally the number believed drowned.