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 when their boat sank off Libya.
The person who made the latest distress call “said that there are over 300 people on his boat and it is already sinking and he has already reported fatalities, 20 at least”, the IOM’s Federico Soda wrote in an email reported by AFP news agency.
The Maltese navy told the BBC that there were many new incidents involving rescues being co-ordinated off Libya by the Italians, but it was unclear if these included the one reported by the IOM.
The EU’s foreign policy chief Federica Mogherini said Europe had a “political and moral duty” to act in the migrant crisis in the Mediterranean.
“The Mediterranean is our sea and we have to act together as Europeans… 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.