A policeman (R) gives instructions to migrants after they disembarked from the expedition vessel Phoenix in the Sicilian harbour of Augusta, Italy, June 7, 2015. [Photo/Agencies]

ROME/LONDON - An international rescue fleet plucked almost 5,900 migrants from rickety boats making the perilous sea crossing for North Africa to Europe on Saturday and Sunday, Italy's coastguard said.

The British warship Bulwark assisted in picking up more than 1,000 refugees, including 10 pregnant women, the Ministry of Defence said.

The Italian coastguard, which coordinates rescue efforts from Rome, said British, Swedish, Spanish and Italian ships and a merchant vessel had all been called upon to go to the aid of 15 different boats on Sunday, rescuing 2,400 people in all.

On Saturday, 3,500 migrants were rescued about 45 miles from the Libyan coast.

The tide of migrants and refugees risking the often deadly sea crossing to reach Europe from Africa is on the rise this year and the UN refugee agency estimates more than 1,800 have drowned. About 800 perished in a single shipwreck in April.

In response, the EU has bolstered its presence in the Mediterranean, but it is still debating how to handle the refugees and migrants once they are ashore.

All those rescued are being taken to Italian ports, which is creating tension between the government and local politicians from opposition parties, especially from the anti-immigrant Northern League, who say they cannot welcome any more migrants.