Almost 800 illegal immigrants arrived in southern Italy aboard just three boats on Sunday, in one of the largest daily influxes of third world refugees that Italy has seen.
Italy believes many of the migrants set sail from Libya and the Italian Foreign Ministry said it had called in the Libyan ambassador for talks tomorrow.
Port officials said 478 migrants crammed on a 25-metre-long boat landed on the island of Lampedusa overnight - the biggest number to arrive there on a single vessel.
It was not immediately clear where the group came from.
A further 169 immigrants reached Lampedusa after daybreak while a boat carrying 130 migrants from Somalia and Ethiopia came ashore in Sicily, a naval spokesman in Palermo said.
Italian Prime Minister Mr Silvio Berlusconi met Libyan leader Mr Muammar Gaddafi last month to discuss ways of stemming an upsurge of migrants, who are called "clandestini" in Italian.
The Foreign Ministry said in a statement that it had ordered Italy's ambassador in Tripoli to urge the Libyan government to cooperate fully in the fight against human trafficking.