At least 8,565 migrants died on land and sea routes worldwide last year, the highest number since the U.N. migration agency began counting deaths a decade ago.

The biggest increase was on the treacherous Mediterranean Sea crossing, to 3,129 from 2,411 in 2022, the International Organization for Migration said Wednesday. However, that was well below the 5,136 deaths recorded on the Mediterranean in 2016 as huge numbers of Syrians, Afghans and others fled conflicts in their homelands toward Europe.

The 2023 count was nearly 20% more than the previous year. Most of the deaths last year, about 3,700, were people who drowned. The count also includes migrants who vanished — often while trying to cross by sea — and are presumed dead even if their bodies were not found.

The Geneva-based migration agency cautioned that their count likely underestimates the true death toll and said improved data collection methods are a factor in its calculations.

“Every single one of them is a terrible human tragedy that reverberates through families and communities for years to come,” IOM Deputy Director General Ugochi Daniels said in a statement.

Overall, the biggest jump in deaths in recent years was in Asia, where 2,138 migrants died last year, 68 more than in 2022. That was primarily because of increased deaths among Afghans fleeing to places like neighboring Iran and among Rohingya refugees on maritime routes, IOM spokesperson Jorge Galindo said in an email.

IOM said a record number of deaths also occurred in Africa last year — 1,866 — mostly in the Sahara Desert and along the sea route to the Canary Islands.