Widespread abuse of immigrants has resulted in many choosing to go home rather than contintuing in Libya.
More than 15,000 migrants have returned home from Libya through a voluntary programme since the beginning of 2018, the International Organization for Migration (IOM) said on Friday.
"So far this year, more than 15,000 migrants were able to return home to 32 countries across Africa and Asia with support from the European Union Trust Fund," IOM said on its Libya Facebook page.
IOM has a "voluntary return hotline" number on its Facebook and Twitter accounts "for migrants stranded in Libya who wish to return to their countries of origin".
The IOM accelerated the pace of departures at the end of last year after CNN television aired footage of African markets being sold as slaves in Libya.
In 2017, IOM repatriated about 20,000 migrants through its voluntary return programme and the UN agency was hoping to increase the number to 30,000 by the end of this year.
Abuse of migrants is widespread in Libya, where they have been taken advantage of in the chaos which has reigned since the 2011 ousting of dictator Muammar Gaddafi.
People smugglers have taken advantage of the turmoil, putting African migrants seeking to reach Europe at greater risk.
Many migrants, intercepted or rescued at sea, find themselves held in detention centres where they face dire conditions.