New distress calls have been received from migrant boats in the Mediterranean, as EU ministers met in Luxembourg to discuss thecrisis.
Italy and Malta said they were working on rescues of at least two boats in distress with hundreds on board.
The EU added the migrants issue to its agenda after a boat sank early on Sunday with hundreds feared drowned.
EU ministers are under pressure after last year's decision to scale back search-and-rescue efforts.
Italian PM Matteo Renzi said on Monday that his country was working with Malta to rescue at least two boats in distress.
He said one of the vessels was a dinghy off the Libyan coast with about 100-150 people on board. The other was larger boat carrying 300 people.
The Maltese navy told the BBC that there were a number of new incidents involving rescues being co-ordinated off Libya by the Italians.
The International Organization for Migration (IOM) also said it had received a distress call from a boat sinking in the Mediterranean with at least 300 migrants on board.
The caller said about three boats needed help in international waters and 20 people had died.
But IOM spokesman Joel Millman told the BBC the organisation was still trying to verify the details and it was unclear whether the call was related to the Maltese and Italian rescues.
Earlier, the Greek coastguard said a vessel carrying dozens of migrants had run aground off the island of Rhodes. Three people were killed and 80 rescued, it said.