MADRID (AP) — A Spanish aid organization said Friday that it feared that hundreds of migrants may have died Libya's coast after five bodies were found near two capsized boats while the search for a third vessel reported missing has so far proved futile.

Proactiva Open Arms spokeswoman Laura Lanuza said their vessel was heading north to the Italian port of Catania to hand over the bodies of the five young men found Thursday.

She said that other NGOs are continuing the search for possible victims off Libya's coast.

The U.N. refugee agency said it was "deeply alarmed" by the reports. Both it and Proactiva said they feared the death toll may be much higher as migrant dinghies are normally crammed with around 120 people each.

The agency cited sources from nongovernmental organizations as saying the five floating corpses of young men had been recovered about 14 miles (22 kilometers) off the Libyan coast near two empty and partially submerged rubber dinghies.

Lanuza said the boats were found Thursday morning, north of the Libyan town of Sabratha. The five men of African origin were estimated to be between 16 and 25 years old and appeared to have drowned, she said.

The Red Crescent in Libya, and the Libyan coast guard, said Friday that they had no reports about dead migrants or capsized boats in the 12 miles (20 kilometers) of Libyan territorial waters.

The UNHCR said the latest incidents come after an intense week of arrivals through the Central Mediterranean route with almost 6,000 migrants and refugees rescued in just five days this week.

It said so far this year some 21,903 people had crossed the Mediterranean Sea to European shores.

The agency said that since the beginning of 2017, and excluding the latest incidents, around 590 people have died or have gone missing in crossings.

Last year was the deadliest ever recorded with 5,096 migrants perishing or going missing, according to the UNHCR.

_____

Associated Press writers Aritz Parra in Madrid, and Maggie Michael in Cairo, contributed to this report.