More than 900 migrants have been rescued in one day from three overcrowded boats en route to Europe from North Africa, an Italian coast guard official has said.

All the rescues were carried out on Wednesday (local time) and a body recovered, the official said, with no details about the one death or the migrants' nationalities.

Two Italian coast guard patrol boats and a merchant ship, whose country of origin was not given, saved 328 migrants from a boat in Maltese waters.

A French navy vessel participating in the EU's border control mission Triton picked up 297 people, including 51 women and children.

Another Italian navy ship rescued 286 and picked up one body.

By the numbers: Total migrant arrivals in Italy: 200,000 in 2015, an increase of 30,000 on last year

Total migrant arrivals in Italy: 200,000 in 2015, an increase of 30,000 on last year Syrians make up a third of the migrants, Afghans and Eritreans 10 per cent each

Syrians make up a third of the migrants, Afghans and Eritreans 10 per cent each About 1,800 dead or missing so far compared with 3,500 in 2014

All of the migrants have been or will be brought to Italian ports, the coastguard said.

With Libya engulfed in strife, people smugglers are increasingly free to pack migrants onto unsafe boats, and they are expected to push total arrivals in Italy for 2015 to 200,000, according to an interior ministry projection.

Italy is bearing the brunt of the Mediterranean rescue operation while European Union authorities press other member states to share the burden more fairly through a resettlement quota system for refugees.

Refugees escaping war and political persecution, and economic migrants desperate for a better life have been pouring into Italy this year, with approximately 35,500 arriving there up to the first week of May, the UN refugee agency estimates.

Also including arrivals in Greece, Spain and Malta, a total of 62,500 have reached Europe by boat, with Syrians making up a third and Afghans and Eritreans 10 percent each.

The number of dead or missing this year is about 1,800 compared with 3,500 during the whole of last year, the United Nations High Commissioner for Refugees says.

About 1,800 people have died this year attempting to cross the Mediterranean and reach Europe. ( AFP: Giovanni Isolino )

Reuters