The International Organization for Migration (IOM) on Thursday said that migrants rescued off the Libyan coast "should not be returned to detention" due to security conditions.

"200 migrants now returned to Libyan shore while armed clashes intensify in the capital Tripoli. IOM reiterates that there are no safe ports in Libya and migrants should not be returned to detention," IOM said.

Since early April, the east-based army has been leading a military campaign to take over the capital Tripoli from the UN-backed government.

According to the World Health Organization (WHO), the fighting has so far killed 510 people and injured 2,467 others.

Libya has become a preferred departure point for illegal migrants hoping to cross the Mediterranean Sea into Europe due to insecurity and chaos in the North African country following the 2011 uprising that toppled former leader Muammar Gaddafi.

Migrant shelters in Libya are crowded with thousands of migrants who have been rescued at sea or arrested by the Libyan security services.