The latest operations involved coastguard and other Italian ships, British, Irish and Spanish navy vessels and a boat operated by Malta-based humanitarian organization Moas, the coastguard said.

The rescues lifted to nearly 68,000 the number of migrants to have landed in Italy this year, according to figures compiled by the International Organisation for Migration (IOM).

The unprecedented figure represents a slight increase on the same period last year (63,885 arrivals January 1st-June 30th), which ended with a record 170,000 migrants landing in Italy.

The surge in numbers since the start of 2014 has left Italy's reception facilities, currently housing around 80,000 asylum-seekers and others seeking leave to remain in the country, under severe strain.

The situation is likely to get worse over the summer, when the numbers of boats dispatched by people smugglers usually peaks. Of last year's arrivals, some 100,000 arrived between June and September.

The sharp increase in migrant arrivals has left Italy's centre-left government under constant attack from the country's vocal far-right and some regions are threatening to refuse to house any more migrants.

The crisis has also put Italy at loggerheads with its European Union partners over contested proposals to spread some asylum-seekers across the bloc and moves by neighbouring countries to tighten their border controls to restrict the numbers of migrants travelling out of Italy on their way to northern Europe.

Italy regards these moves as breaching the principles of solidarity and of free movement of people within Europe. On the other side of the debate there is a perception that Italy is not sufficiently rigorous about registering new arrivals at its ports and sending economic migrants back to their countries of origin as a deterrent to others thinking of making the trip.

According to aid groups, just over half of the migrants arriving in Italy have a legitimate claim to asylum, mostly as a result of having fled conflict in Syria or repression in Eritrea.

The civil war in Syria is also seen as being behind a surge in asylum-seekers arriving in Greece, where over 80,000 migrants have arrived this year, three quarters of them on boats which mostly leave from Turkey.

This year has also seen a sharp increase in the numbers of migrants dying during the crossings with over 1,800 fatalities reported en route to Italy and at least 27 off Greece, according to the OIM.