The UN refugee agency (UNHCR) said that as the summer season starts, the number of refugees and migrants attempting to cross the Mediterranean was expected to increase and it called for increased rescue operations.

The Libyan coast guard has brought more than 8,000 people to disembarkation points along the coast this year, it said

Only five people survived the capsizing of a boat carrying 100 people on Tuesday, while the same day a rubber craft with 130 passengers sank, leading to 70 people drowning, UNHCR said.

On Wednesday a boat of refugees and migrants who were rescued reported that more than 50 people travelling with them had perished at sea, it said.

"UNHCR is dismayed at the ever-growing numbers of refugees and migrants losing their lives at sea and is calling for urgent international action to strengthen rescue at sea efforts by all relevant and capable actors, including NGOs and commercial vessels, throughout the Mediterranean," the agency said.

Earlier, Libya's coastguard picked up 443 African migrants on Thursday from three inflatable boats in trouble near its western coast, a spokesman said.

Libya is a main departure point for migrants fleeing wars and poverty trying to reach European countries, though crossings have dropped sharply since last July due to a more active coastguard supported by the European Union.