At least a dozen bodies were retrieved, it said.
Since the beginning of the year, some 3,600, including around 270 women and 187 children, were returned to the North African country, the IOM said.
Like previous ones, those migrants were taken to squalid detention centers in and around Tripoli. Thousands of migrants have already been confined in these centers, mostly run by militias linked to authorities in Tripoli.
In January, a boat carrying Europe-bound migrants capsized in the Mediterranean off the coast of Libya, and at least 43 people drowned, the first maritime disaster this year involving migrants seeking better lives in Europe.
The U.N. migration and refugee agencies have repeatedly called for an “urgent and measurable shift in the approach” to the situation in the Mediterranean, including an end to migrant returns to “unsafe” Libya.
Libya has become the major transit point for African and Arab migrants hoping to reach Europe after the North African country plunged into a bloody civil war following the NATO-backed uprising that toppled and killed longtime ruler Moammar Gadhafi in 2011.
Traffickers have exploited the chaos and often pack desperate families into ill-equipped rubber boats that stall and founder along the perilous Mediterranean route. Thousands have drowned along the way. Traffickers have been implicated in widespread abuses of migrants, including torture and abduction for ransom.
The European Union has over the past years partnered with Libya to prevent migrants from making the dangerous journey by sea to Europe. Rights groups say those efforts have left migrants at the mercy of armed groups or confined in squalid detention centers that lack adequate food and water.
An Associated Press investigation in 2019 found that militias in Libya tortured, extorted and otherwise abused migrants for ransoms in detention centers under the nose of the U.N., often in compounds that receive millions in European money, paid to Libya's government to slow the tide of migrants crossing the Mediterranean.