The Italian government has formally requested aid from the European Union to help it cope with thousands of Tunisians arriving on its shores.
Some 5,000 migrants have landed on the island of Lampedusa in recent days following Tunisia's January uprising.
Meanwhile, unconfirmed reports say at least five migrants died and others are missing after their boat sank.
Witnesses quoted by the AFP news agency said the boat had been rammed by a Tunisian coastguard ship.
Italy's interior minister said the country was seeking some 100m euros (£84m; $134m) from the EU to tackle the influx.
The mayor of Lampedusa has declared a state of emergency and the UN refugee agency has described the situation there as "critical".
Prime Minister Silvio Berlusconi told EU President Herman Van Rompuy in a telephone conversation that the situation "is urgent and concerns all of the European Union", according to a government statement quoted by AFP news agency.
Italy's Interior Minister Roberto Maroni said he had filed a request for funds on Monday.
He also said he had asked for the intervention of the EU's border management agency, Frontex, and placed an additional 200 soldiers on alert to supervise the centres where the migrants are staying.
One such centre on the island - which houses 850 people - has been reopened and thousands have been shipped to Sicily, where there are more facilities.
The International Organization for Migration (IOM) has described the migrants as "a mixed flow" - some were fleeing insecurity in Tunisia, following last month's uprising there, while others were seizing the chance to get to Europe to find work.
Lampedusa Mayor Bernadino Rubeis said on Tuesday: "There is an entire nation trying to escape Tunisia to reach Italy and then to go on to other countries."
Since Tunisia overthrew Zine al-Abidine Ben Ali last month, police patrols along the coast have been patchy.
However, Tunisian officials - under strong pressure from Italy and the EU - have pledged to step up coastal security.
Fears of retribution
The BBC's Jim Muir in Tunis says many people there are puzzled by the upsurge in the number of people trying to get to Italy, as the situation in Tunisia is seen to be stabilising.
Some of those trying to leave are said to be well-dressed and paying over the odds for the trip, our correspondent says - indicating they might be associated with the former regime and trying to avoid retribution.
But most are believed to be economic migrants taking advantage of a security loophole, he adds.
Laura Boldrini, of the UN refugee agency (UNHCR) who is on Lampedusa, told the BBC World Service that the situation on the island was "critical".
She said conditions had improved slightly since the island's reception centre re-opened on Sunday but it was important to move people to other reception centres in Italy.
Ms Boldrini said the migrants were either saying they wanted to escape "insecurity" in Tunisia or had left to look for jobs in Europe.
She added that some planned to travel on to France and other European countries to be reunited with family members already there.
"This influx is affecting many other countries, not only Italy."
The Italian request for funds came as EU foreign policy chief Baroness Ashton visited Tunis.
She said the EU wanted to be Tunisia's "strongest ally" in pushing towards democracy and announced new EU help of 17m euros (£14m; $23m).
Meanwhile, alleged survivors of the sunken boat told AFP that a Tunisian coastguard ship rammed their boat on Friday as it was making its way to Italy.
"The boat... was carrying 120 passengers - 85 people were saved, five died and 30 are still missing," 23-year-old Ziad Ben Abdaalah is reported to have said.
Coastguard officials in Zarzis contacted by AFP confirmed that a boat had sunk but blamed it on the poor condition of the boat and declined to make any further comment.