The Geneva-based agency had warned Tuesday that this year's death toll was likely to exceed the 3,771 deaths reported for the whole of 2015.
"We're receiving more reports of deaths in the Med," spokesman William Spindler tweeted Wednesday. "We can now confirm that at least 3,800 people have died, making 2016 the deadliest ever."
Scores of migrants have been drowning each week as the fragile and often overcrowded boats they travel on capsize or sink, the U.N. agency said. It blamed bad weather, flimsy boats and the fact that migrants fleeing war and poverty are increasingly taking the hazardous central Mediterranean route from Libya to Italy in an attempt to reach Europe.
A deal between the European Union and Turkey largely closed off the eastern route earlier this year.
About half of the 327,800 migrants who crossed the Mediterranean this year did so using the central route, where about 1 in every 47 people dies. By comparison, the overall death rate for the whole Mediterranean last year — when more than a million people arrived in Europe — was one in 269 crossings.
The U.N. agency also said that smugglers have been changing their tactics, arranging mass embarkations of thousands of people at once.
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