Dozens of refugees were feared missing after their boat sank off Libya on Wednesday, a spokesman for the country's naval forces said, amid signs of a sharp increase in the number of people attempting the dangerous crossing from North Africa to Europe.
Earlier Italian officials said their coastguard and navy vessels had rescued 1,361 refugees on Wednesday from boats and rubber dinghies in the southern Mediterranean.
The Libyan spokesman, Ayoub Qassem, said naval guards had intercepted one boat carrying 120 refugees off the coast near Sabratha and had also managed to rescue 32 from the boat which sank. It was not known exactly how many people were missing.
More than 16,000 people have made the crossing from North Africa to Italy in the first three months of 2016, some 6,000 more than in the same period last year.
The number of new arrivals is expected to climb further in coming months as warmer, more stable weather kicks in, making it easier for people traffickers to put the boats to sea.
The Italian Coastguard said that after saving some 3,680 people over the past three days a further 350 refugees, most believed to be minors, had been spotted on a boat off Sicily and an operation was under way to bring them ashore.
Italian officials have also warned that a deal to limit the number of refugees travelling to Greece could increase the flows through Libya to Italy.
However, up until now, the vast majority of refugees using the Mediterranean route have continued to come from sub-Saharan Africa, with no significant increase in the number of Syrians, Afghans or Iraqis, who have mostly been using the Greek route.
Hundreds of thousands of refugees have reached Italy in recent years, looking for a better life in the European countries.