Italian riot police fired tear gas and water cannons in Rome on Saturday as violent protesters hijacked a peaceful demonstration against corporate greed, smashing bank windows, torching cars and hurling bottles.

Elsewhere, hundreds of thousands nicknamed "the indignant" marched without incident in cities across Europe, as the Occupy Wall Street protests, which started in New York, linked up with long-running demonstrations against European governments' austerity measures.

Heavy smoke billowed in downtown Rome as a small group broke away and wreaked havoc in streets close to the Colosseum and elsewhere in the city.

Clad in black with their faces covered, protesters threw rocks, bottles and incendiary devices at banks and Rome police in riot gear. With clubs and hammers, they destroyed bank ATMs, set trash bins on fire and assaulted at least two news crews from Sky Italia.

Riot police charged the protesters repeatedly, firing water cannons and tear gas. Around 70 people were injured, according to news reports, including one man who tried to stop the protesters from throwing bottles.

Rome Mayor Gianni Alemanno blamed the violence on "a few thousand thugs from all over Italy, and possibly from all over Europe, who infiltrated the demonstration." Some Rome museums were forced to close down and at least one theater canceled a show.

Italian news agency ANSA said four people from an anarchist group were arrested Saturday with helmets, anti-gas masks, clubs and hundreds of bottles in their car.

Largely peaceful demonstrations, meanwhile, were held in cities across Canada.

Protests held in London, Lisbon

Elsewhere, bright autumn sunshine and a social media campaign brought out thousands across Europe.

In Spain, the Indignant Movement that began around-the-clock protest camps in May which lasted for weeks, held evening marches Saturday that converged on Madrid's Puerta del Sol plaza.

Other Spanish cities including Barcelona, Seville, Valencia and Malaga hosted similarly well-attended gatherings.

Portuguese protesters angry at their government's handling of the economic crisis pushed against police lines in Lisbon, but officers stopped them from storming parliament. Portugal is one of three European nations — along with Greece and Ireland — that has had to accept an international bailout.

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Wikileaks founder Julian Assange, addresses the media during the Occupy London Stock Exchange demonstration in London on Oct. 15. (Elizabeth Dalziel/Associated Press)

In Frankfurt, continental Europe's financial hub, 5,000 people protested at the European Central Bank, with some setting up a tent camp in front of the ECB building.

Wikileaks founder Julian Assange spoke to protesters outside St. Paul's Cathedral in London, calling the international banking system a "recipient of corrupt money."

The London demonstration swelled to several thousand people by early evening, and police said three were arrested. While protesters erected tents and gathered blankets, food and water to settle down for the evening, police urged them to leave, saying cathedral staff needed to prepare for Sunday services.

Demonstrations smaller in Asia

The Greek capital of Athens has seen near-daily strikes and protests as the government fights to avoid bankruptcy, and Saturday was no different. Some 2,000 rallied outside parliament against a new austerity package being voted upon on Thursday, while teachers and civil servants held marches elsewhere in the city. In Thessaloniki, Greece's second city, 3,000 took part in a peaceful protest.

In South Africa, about 50 activists rallied outside the Johannesburg Stock Exchange to demand more jobs, free education and universal healthcare.

Support for the anti-capitalist protest movement was light in Asia, where the global economy is booming. About 300 people turned out in Sydney, while another 200 chanted anti-nuclear slogans outside the Tokyo Electric Power Co., which operates the tsunami-hit Fukushima Dai-ichi nuclear plant. In the Philippines, 100 people marched on the U.S. Embassy in Manila.

Arrests in New York

New York police say more than 80 people have been arrested in the latest demonstrations there against corporate greed.

Two police officers suffered injuries and had to be hospitalized Saturday. One had a head injury.

Police spokesman Paul Browne said 42 people were arrested in Times Square after being warned repeatedly to disperse; three others were arrested earlier while trying to take down police barriers.

Two dozen people were arrested at a Citibank branch when they refused a manager's request to leave. Most were detained for trespassing. Five others were arrested for wearing masks.

About 10 people were loaded into a police van at a Manhattan park after midnight after police announced the park had closed.