CAIRO >> A migrant boat has capsized off the Libyan coast, leaving at least 35 people dead or presumed dead, the U.N. migration agency said Saturday. It was the second tragedy in less than a week involving migrants departing from North Africa to seek a better life in Europe.

The shipwreck took place Friday off the western Libyan city of Sabratha, a major launching point for the mainly African migrants making the dangerous voyage across the Mediterranean, said the International Organization for Migration.

The IOM said the bodies of six migrants were pulled out while 29 others were missing and presumed dead. It was not immediately clear what caused the wooden boat to capsize.

Friday’s tragedy was the second shipwreck off Libya in less than a week with a total of at least 53 Europe-headed migrants dead or presumed dead, according to the IOM.

On Tuesday, a wooden boat carrying at least 20 migrants capsized off the western town of Sorman. Two migrants were rescued and at least 18 were pronounced dead with six bodies retrieved, the U.N. migration agency said.

“Dedicated search and rescue capacity and a safe disembarkation mechanism are urgently needed to prevent further deaths and suffering,” the IOM said.

Investigators commissioned by the United Nations’ top human rights body found evidence of possible crimes against humanity committed in Libya against migrants detained in government-run prisons and at the hands of human traffickers.

Earlier this month, more than 90 people in an overcrowded boat drowned in the Mediterranean Sea, days after they left Libya, according to the Doctors Without Borders aid group.

Migrants regularly try to cross the Mediterranean from Libya in a desperate attempt to reach European shores. The country has emerged as the dominant transit point for migrants fleeing war and poverty in Africa and the Middle East.

Human traffickers in recent years have benefited from the chaos in Libya, smuggling in migrants across the oil-rich country’s lengthy borders with six nations. The migrants are then typically packed into ill-equipped rubber boats and set off on risky sea voyages.

At least 476 migrants died along the Central Mediterranean route between Jan. 1 and April 11, according to the IOM.

Many of those who have been intercepted and returned to Libya — including women and children — are held in government-run detention centers where they suffer from abuse, including torture, rape and extortion, according to rights groups.