The number of migrants sailing from Africa to Italy resembles a "biblical exodus", the head of the Italian navy said yesterday.
Adml Giuseppe De Giorgi said his ships had rescued 18,546 migrants, including Syrians and sub-Saharan Africans, since October, following the deaths of 364 migrants when their boat caught fire.
The peak came this week when 4,000 were intercepted by the navy in 48 hours.
Angelino Alfano, Italy's interior minister, has claimed up to 600,000 migrants are preparing to sail from Africa as weather improves in the Mediterranean.
Adml De Giorgi said Italy was deploying large helicopter carriers, frigates, drones and helicopters carrying infra-red sensors to monitor the seas.
"The phenomenon is enormous, each migrant ship now contains 200 to 300 and they are also coming in rough seas, so we need frigates to pick them up," he said.
"This is a biblical exodus and turning them back is not part of our mission."
The largest boat intercepted was carrying 553 migrants, he said.
Adml De Giorgi said "well-trained" traffickers were sailing from Egypt in "mother ships" towing smaller boats carrying hundreds of migrants, which they released in the middle of the Mediterranean.
In November, an Italian submarine that was on exercises in the area had followed a mother ship for 48 hours.
When the mother ship untied a migrant vessel and pulled away at speed, the submarine surfaced and an Arabic-speaking naval officer told migrants to wait to be picked up.
A frigate then chased the mother ship and halted it with machinegun fire. "They were good sailors, not scared," said Adml De Giorgi, adding the arrest of the traffickers was acting as a deterrent. "It made them understand we are serious," he said.
Sixty traffickers had now been handed over to Italian prosecutors by the navy, he added.
Admiral De Giorgi said that 42,925 migrants made it to Italy by sea in 2013, a 224 per cent rise on the previous year, but he denied suggestions that more were sailing because the navy was now waiting to pick them up.
"The boom is not due to the navy, but there are fewer deaths now," he said.