At least 73 migrants have been lost and are now presumed dead after their boat capsized off the coast of Libya, the International Organization for Migration (IOM) said on Wednesday.  

"At least 73 migrants are reported missing and presumed dead following a tragic shipwreck off the Libyan coast yesterday according to @UNmigration in Libya," the organization tweeted.

"Seven survivors who made it back to Libyan shores in extremely dire conditions are currently in the hospital," the UN migration agency said.

Around 80 people in total were on board the boat, which left the coastal town of Qasr Alkayar in western Libya, on Tuesday, in an attempt to reach Europe, the IOM specified.

In April last year, up to 100 migrants died in the Mediterranean waters after the boat carrying them from Libya got shipwrecked, the UN High Commissioner for Refugees Flippo Grandi said. 

Migrants trying to reach European shores regularly use Tunisia and Libya as key departure points, often using damaged vessels.

Read: Borrell: Turkey's Influence in Libya Affects Mediterranean Migration

Last year, Libya's authorities arrested 542 people attempting to illegally migrate from its shores to Europe in inflatable boats; most were from Bangladesh, according to an AFP photographer.

Libya has become a transit point for illegal migrants who head to Europe ever since the NATO-backed uprising that toppled and killed President Muammar Gaddafi and the start of the civil war in 2011.

Read: Europe's Detention Hell-Hole in Libya: Migrants Raped, Tortured, Beaten

Since 2014, more than 25,000 migrants have been reported dead or missing in the Mediterranean region, according to IOM.