Frontex said a total of about 33,000 migrants were detected trying to enter the 27-nation bloc in the first three months of the year, more than double the figure for the same period of 2010. Over two-thirds of this number - 22,600 people - were found at Italy's borders, mainly in the area around the tiny southern island of Lampedusa, said Frontex deputy director Gil Arias Fernandez.
Greece, whose frontier with Turkey was previously the main entry for people seeking to cross into the EU, saw 7,200 illegal entries in the same time period compared with 13,100 in January-March 2010 after border patrols were strengthened, according to Frontex.
More than 41,000 migrants have reached Lampedusa since the start of the year, including over 1,600 last weekend.
After a surge of Tunisian arrivals in early 2011 following the unrest in the North African country that toppled longtime leader Zine El Abidine Ben Ali from power, most migrants now reaching Lampedusa and nearby islands have set sail from Libya.
Most hail from sub-Saharan Africa and are more likely to gain political asylum than Tunisians, who are considered economic migrants.
Fernandez said that while it was difficult to predict what would happen in the rest of the year, "the situation will remain quite dramatic in the central Mediterranean."
Eu leaders are due to discuss possible revisions to the EU's Schengen passport-free travel system for countries that are unable to control illegal immigration.
The influx of illegal migration to Europe from North Africa has sparked rows between EU states, notably Italy and France, into which many migrants had tried to cross after being granted six-month visas by Italy's interior ministry.