More than 2,500 migrants have drowned in the Mediterranean while attempting to cross into Europe so far this year, the U.N. Refugee Agency says, with at least 880 drowning in the past week alone.

William Spindler, spokesman for the agency, said 2,510 people have died making the perilous crossing so far this year, compared to 1,855 in the first five months of 2015 -- an increase of 35 percent. Fewer than 60 died in the same period in 2014.

Most migrants in the recent wrecks were from Syria, Afghanistan, Iraq and Pakistan, the U.N. refugee agency said last week.