Scuffles broke out in Rome as tens of thousands of people marched through Italy's capital to protest against unemployment and government cuts.
They are also objecting to big construction projects they say take money away from social services.
Demonstrators threw bottles at a police van and eggs at banks and the economy ministry.
Police intervened to keep right-wingers opposed to the protest away from the marchers.
The protest comes as Prime Minister Enrico Letta is trying to hold together his shaky left-right coalition government and struggling to lead Italy out of its worst post-war recession.
Mr Letta's 2014 budget, unveiled on Tuesday, has become a focal point of discontent.
Unions are complaining about freezes on public sector salaries.
They also are objecting to what they say is an insufficient easing of the tax burden on workers.
Youth unemployment is at an all time high at 40.1%.
Organisers said at least 70,000 people joined the march that started in Piazza San Giovanni on the south side of the city and snaked its way through a mostly deserted centre.
Many shops along the route were closed as a precaution for fear the demonstration could turn violent.
A similar protest two years ago left several people were injured as protesters smashed windows and set fire to cars.
The mostly young demonstrators held up banners against unemployment, lack of affordable housing and the planned TAV high-speed train link to France.
Opponents of the project say that as well as environmental concerns, the money to build the high-speech train should be used to help the poor and unemployed.
Immigrants seeking asylum also joined the demonstration, holding banners reading "Lampedusa."
At least 4,000 police were on duty, securing the route of the demonstration, particularly near the Industry Ministry andthe Bank of Italy.
Police said they had confiscated teargas canisters and rocks from some of the demonstrators' backpacks.
They also said they found rocks and chains hidden behind bushes along the route of the demonstration.
Police said 14 people, several from anarchist movements, had been detained at the border with France and suspected of planning to disrupt the demonstration with violence.
Meanwhile, a Milan court has ruled that former Prime Minister Silvio Berlusconi should be barred from holding public office for two years following a conviction for tax fraud.
Because Mr Berlusconi is a senator however, the court's decision will have no immediate effect.
Expulsion requires a Senate vote which is expected to follow next month.
Mr Berlusconi's lawyers who can appeal to the supreme court had asked for a one-year ban, the minimum under the relevant law.
The Senate is dominated by Berlusconi opponents from both the left and the anti-establishment 5-Star Movement and is expected to vote to strip him of his seat.
Losing his seat in the Senate would deprive Mr Berlusconi of his parliamentary immunity from arrest.
Italy's supreme court on 1 August upheld a tax fraud conviction against the centre-right leader.
It rejected his final appeal against an earlier four-year jail sentence but commuting it to a year.
If the Senate expels him, he will spend the year either under house arrest or in community service.
He is currently fighting a conviction for paying for sex with a minor among other legal cases.