Silvio Berlusconi survived yet another threat to his tenure as Prime Minister of Italy in Tuesday''s vote, though his struggling center-right government has been severely weakened.

The result reinforced Berlusconi''s reputation as one of the great survivors of Italian politics but left him badly undermined, without the numbers in parliament to ensure stability at a time of big economic challenges and a menacing euro zone debt crisis.

Berlusconi''s survival was ensured with 314 votes against 311 in the lower house of parliament.

Vote counting after an acrimonious debate was briefly interrupted by a scuffle between deputies from rival camps.

Pier Luigi Bersani, head of the opposition Democratic Party, said Berlusconi''s survival was a Pyrrhic victory.

"You, prime minister are no longer in a position to govern," he told parliament.

Riot police blocked off the center of Rome and clashed with protesters who threw firecrackers and paint bombs at the Senate and oranges at the economy ministry.

After a year overshadowed by corruption and sex scandals and an acrimonious split with former ally Gianfranco Fini that cost him a secure parliamentary majority, the result offered at least a temporary lifeline to the 74-year-old premier.

Berlusconi has repeatedly defied skeptics, shrugging off a string of gaffes and scandals to win three elections and transform Italy''s political landscape since gaining power for the first time in 1994, but he has polarized Italians.

Thousands of students, workers and other government opponents staged other protests around the country on Tuesday.

Had Berlusconi lost in the lower house following a clear win in the Senate earlier on Tuesday, he would have had to resign, potentially opening the way to early elections more than two years before they are due in 2013.

The result was secured after a fevered campaign of back room deals, in which opposition accusations of vote-buying and corruption have been answered by fierce denials and counter-accusations of treachery.