At least 73 migrants are missing and presumed dead after their boat sank off the Libyan coast, according to the UN's International Organization for Migration (IOM).

Only seven people survived Tuesday's shipwreck but are in "extremely dire conditions" in hospital.

So far 11 bodies have been recovered by the Libyan Red Crescent and police.

The boat was heading to Europe on a route the IOM has called "the world's deadliest migratory sea crossing".

More than 130 people have already died this year making the dangerous journey over the Mediterranean Sea.

The IOM added that more than 1,450 deaths were recorded by its Missing Migrants Project last year.

"This situation is intolerable," said Safa Msehli, a spokesperson for the group.

Ms Msehli said more efforts were needed to "increase search and rescue capacity, establish clear and safe disembarkation mechanisms as well as safe and regular pathways to migration to reduce dangerous journeys".