The Italian Navy said late on Friday it has recovered 45 corpses of migrants and saved 135 shipwrecked amid continuous arrivals of refugees and asylum seekers by the Mediterranean Sea.

The Italian Navy also added on Twitter that it was continuing the search for those missing.

On Wednesday, five bodies were recovered and 540 migrants saved, including a nine-month orphaned Nigerian girl, after their overcrowded boat capsized.

Another disaster occurred on Thursday, when a migrant boat capsized 35 nautical miles north of the Libyan city of Zuwara, with 20 to 30 people feared to have lost their lives.

According to Rai state television, an estimated 10,000 migrants have been rescued so far this week in the southern Mediterranean by naval forces involved in the European Union (EU) naval mission EUNAVFOR MED and EU borders agency Frontex.

Some 4,100 were saved on Thursday alone, while another 1,900 were rescued on Friday, and dozens were feared missing, the Italian coast guard said in a statement.

Tens of thousands of migrants keep departing from the Libyan coasts, trying to reach Europe through the perilous crossing, and their number has surged following the recent closure of the so-called Balkan route.

More than 40,500 migrants have reached Italy by sea from the beginning of this year to May 26, according to the United Nations refugee agency UNHCR. At least 1,512 were reported dead or missing up to the same date.

Federico Fossi, an Italian spokesperson of the UNHCR, told Xinhua on Friday that most of the migrants who arrived this year were from Sub-Saharan Africa. Among those who reached Italy between January 1 and April 30, 16 percent were Nigerians, 10 percent Gambians and 9 percent Somali, he said.