More than 3,770 migrants and refugees died in 2015 trying to reach Europe by crossing the Mediterranean Sea, making the year the deadliest on record for those seeking sanctuary from conflict and poverty, an international migration group said on Thursday.

Most of those deaths occurred along a perilous central Mediterranean route used by smugglers operating out of Libya, according to the International Organization for Migration.

The deadliest month was April, when nearly 1,250 migrants died, some 800 of whom were on board an overcrowded ship that capsized off the Libyan coast, the IOM said.