Youths fought with policemen in Rome today as Premier Silvio Berlusconi survived the first of two parliamentary votes of confidence.
Berlusconi survived the confidence vote in the Senate, but still faces a second, less certain, ballot in the lower house.
Mr Berlusconi had been expected to win the Senate vote on a motion in support of the government that had been brought by his allies. The vote was 162-135.
The showdown in parliament follows a dramatic fallout with his former closest ally, Gianfranco Fini.
The break-up potentially deprives Mr Berlusconi of a majority in the lower house, and that vote later today will hang on a few undecided MPs.
Mr Berlusconi has said he is confident he will win both votes.
Police said that tens of thousands of protesters rallied across Italy to demand a change of government as parliament met.
Protest organisers estimated the number in Rome alone at 100,000.
"Let's hope above all that the government falls today. It's a government that's not good for young people and doesn't think about the future," said Victor Hugo Santos, 17, as he protested on a square in central Rome.
Protesters marched along a road through the Roman Forum, hanging Communist Party flags from the Roman statues and setting off smoke flares.
Among the protesters were many students, who are up in arms over an overhaul of the university system announced by Berlusconi's government.
"Summing up what's wrong with Berlusconi would be a very long list! But basically he hasn't managed to cope with the economic crisis," said Andrea.
"His private life has distracted him from dealing with the good of the state," said Andrea, referring to Berlusconi's numerous sex scandals.
Silvia, a teacher, said: "I don't see a future for young people. I'm not just hoping that the government goes home but that a radically new one is formed."
The protesters were mainly students but there were also residents from the town of Terzigno near Naples, which has been hit by a garbage crisis in recent weeks, as well as from earthquake-struck city of L'Aquila.
L'Aquila was devastated by an earthquake last year that killed more than 300 people and many inhabitants say help has been slow in coming.
"We're here to say that it isn't right to vote for the confidence in a government that after carrying out cosmetic operations on our city has now abandoned it," said Ilia Antenucci from a L'Aquila campaign group.
Luciano Castellano, 69, said: "I'm here for my grandchildren, for an honest future with serious foundations.
"The government is playing with the emotions of the people," he said.
Protest marches began in different parts of the city and assembled on Piazza Venezia. Some of the placards brandished by protesters read: "United Against the Crisis" and "If You Don't Fall Yourselves, We'll Be Your Banana Skin."
A small group of protesters in Milan broke into the stock exchange building and unfurled a banner reading: "You're a bunch of racist profiteers."
Students staged a brief sit-in on the landing strip in Palermo airport and some 3,000 marched through the centre of Catania in Sicily.
There were also protests in Bari, Cagliari, Genoa, Naples and Turin.