Rome's worst street violence in years injured 135 people and caused damage of €1 million to public property, according to officials, as the clashes ignited a political row.
Italy’s Prime Minister has said those responsible for yesterday’s violence in Rome must be identified and punished.
Silvio Berlusconi described the rioting as "a very worrying sign for civil society”. He said: “They must be condemned by everyone without reservation".
The protest was one of many staged around the world to show solidarity with the Occupy Wall Street movement in the United States, venting anger over years of economic and financial crisis since a global credit boom went bust in 2007.
The demonstration began peacefully but turned violent when hundreds of hooded demonstrators known as "black blocs," who had infiltrated the larger group, set cars and garbage bins on fire.
Protesters torched several cars, smashed the windows of banks and shops and set alight a military depot building in the city centre. The confrontation in St John Lateran square lasted for four hours.
Out of the injured 105 are officers and 30 are protesters, two of whom have had fingers amputated due to exploding smoke bombs, ANSA news agency reported.
Earlier reports had put the total number of injured people at 70.
"We have to act with appropriate toughness against these animals," Mayor Gianni Alemanno said, as he visited the area around St John Lateran square near the city centre.
Interviewed by ANSA in hospital, a police officer who fled from his van shortly before it was set on fire by protesters at the height of Saturday's clashes said he had never seen violence on this scale.
"I've done protests but I've never seen anything like this. Luckily I had my helmet on, otherwise I'd be dead," said the officer, who was not named.
"I couldn't move forward or back. They broke my side mirror and managed to open one of the doors. Then I don't remember anything. I ran away," he said.
Allies of centre-right Prime Minister Silvio Berlusconi rounded on left-wingers, warning of violent extremists in their midst.
"The violent left wants to destroy and kill," read a headline in the Padania newspaper of the Northern League party, a ruling coalition member.
Opposition forces meanwhile called for a review of security measures.
"The government has to explain in detail how it's possible that such a high number of vandals went unnoticed by the interior ministry," said Italo Bocchino from the right-wing opposition Future and Freedom for Italy party.
"Silence implies complicity and raises suspicion," he said.
Anti-Wall Street protestors march to Times Square
Thousands of anti-Wall Street protesters rallied in New York's Times Square, buoyed by a global day of demonstrations in support of their month-long campaign against corporate greed.
Inspired by the Occupy Wall Street movement, yesterday’s protests started in Asia and rippled through Europe back to the United States and Canada.
Protesters fed up with economic inequality took to the streets in cities from Washington, Boston and Chicago to Los Angeles, Miami and Toronto.
After weeks of intense media coverage, the size of the US protests have been smaller than G20 meetings or political conventions have yielded in recent years. Such events often draw tens of thousands of demonstrators.
In New York, where the movement began when protesters set up camp in a Lower Manhattan park on 17 September, organizers said the protest grew to at least 5,000 people as they marched to Times Square from their makeshift outdoor headquarters.
They are angry that US banks are enjoying booming profits after getting bailouts in 2008, while many people are struggling in a difficult economy with more than 9% unemployment and little perceived help from Washington.
Around 5,000 people marched through the streets of Los Angeles and gathered peacefully outside City Hall.
The Occupy Wall Street movement has been gathering steam over the past month, culminating with yesterday’s action.
In Toronto, a couple of thousand people gathered peacefully and started to set up a camp in one of the city's parks. Protesters in Washington marched through the streets.
Over 1,000 people turned out to protest over austerity in Dublin.
An alliance of trade unionists, community groups, campaigns against cuts, and left wing groups marched from Parnell Square to the Merrion Hotel where the EU-IMF troika are staying during their visit.
