MISRATA, Libya (Reuters) - Fifteen migrants have died in a boat off the Libyan coast after spending 12 days at sea without food or water, an Egyptian survivor said on Tuesday.

Only 10 migrants from the capsized boat survived, all of whom were suffering from severe dehydration, Othman Belbeisi, head of the U.N. migration agency IOM in Libya, said on Twitter.

The owner of a beach chalet found the migrants washing up on the shore near the city of Misrata and called authorities, who brought them to the Red Crescent relief service and hospitals, residents said.

“We were 25 migrants on a boat ... We set off from (the western Libyan town of) Sabratah and we were at sea for 12 days without food and water,” the survivor said. “Fifteen have died.”

The survivors had been brought to a detention center and doctors and emergency teams are on the way, Belbeisi said.

No more details from authorities were immediately available.

Libya’s western coast is a departure point for mainly sub-Saharan African migrants fleeing wars and poverty and hoping to build new lives in Europe.

But the number of migrants reaching Italy has fallen sharply since last year as smuggling networks inside Libya have been disrupted and the European Union has stepped up efforts to increase Libyan coastguard patrols.