Italy says 4000 immigrants have reached its shores by boat in the past two days.
"The landings are non-stop and the emergency is increasingly glaring," Interior Minister Angelino Alfano told Rai Uno public radio on Wednesday.
"Right now, two merchant ships are rescuing two boats with 300 and 361 people aboard," he said.
Mr Alfano estimated that 15,000 migrants crossing the Mediterranean had been rescued so far this year.
Italy reported an increase of 60 percent in asylum claims last year - mainly people fleeing the war in Syria.
Operation Mare Nostrum (Our Sea), a Latin reference to the Mediterranean, began after more than 400 migrants from Eritrea and Syria perished in twin tragedies off the coast of Italy in October 2013.