The International Organization for Migration (IOM) says it has received a distress call from a sinking boat with 300 migrants in the Mediterranean.
Some 20 people are reported dead, an IOM spokesman said.
The caller said about three boats needed help in international waters.
EU ministers are due to meet in Luxembourg later on Monday to discuss the migrant crisis after hundreds of people drowned at the weekend after their boat sank off the coast of Libya.
“We have a political and moral duty to exercise our role. The Mediterranean is our sea and we have to act together as Europeans. It is also [in] our interest, [in that] of our credibility; the European Union was built and is built around the protection of human rights, human dignity and the life of human people – we need to be consistent in that.”
Some southern European nations say the EU’s credibility is now at stake after last year’s decision to scale back search-and-rescue efforts.
The UN says the route from North Africa to Italy and Malta has become the world’s deadliest.