Italy is already grappling with a mass influx of immigrants from Tunisia since the fall of its veteran ruler but Frattini said that would be nothing compared to the number of immigrants that could flee neighbouring Libya.

"There would be an exodus of biblical proportions, a problem that Italy cannot, must not underestimate," Frattini told the Corriere della Sera daily.

"We know what awaits us when the Libyan regime falls: a wave of 200-300,000 immigrants. That would be ten times the number of Albanians in the 1990s" who headed to Italy following the demise of the communist regime in Tirana.

Libya shut down illegal immigration flows across the Mediterranean to Italy after signing a friendship treaty with its former colonial overlord in 2008 that facilitated massive investments between the two countries.

The ouster has been fuelled by the arrival of thousands of Tunisians on the Mediterranean island of Lampedusa since Zine El Abidine Ben Ali was toppled last month.

The boatloads of immigrants have overwhelmed authorities on the tiny island and prompted Italy to appeal for emergency funds from the European Union. Italian Prime Minister Silvio Berlusconi has developed close ties with Kadhafi, with Libya accounting for 13 percent of Italy's gas supplies and almost a quarter of its oil. But the growing turmoil in Libya led to the halt of gas supplies on Tuesday after Italy's ENI suspended some of its operations in the energy-rich state.

Frattini said it was hard for the government in Rome to envisage a scenario without Kadhafi, who came to power in 1969, at the helm in Tripoli.

"The problem is that, to an extent, Kadhafi is Libya. We don't know anything else. There are no other politicians or political parties. And at the moment, it is impossible to imagine a future after him," the foreign minister said.

The anti Kadhafi uprising has sent shockwaves through the Italian business world, with the stock market in Milan suffering sharp drops this week, mainly due to companies linked to Libya.