Occupy Wall Street protesters shout slogans during a protest at Times Square in New York Oct 15, 2011. [Photo/Agencies]

ROME - Hundreds of people camped out in London, Frankfurt and Amsterdam on Sunday after clashes in Rome in worldwide protests seen as the start of a new global movement against corporate greed.

Galvanized by the Occupy Wall Street movement, protests began in New Zealand, touched parts of Asia, spread to Europe, and resumed at their starting point in New York with 5,000 marchers decrying corporate greed and economic inequality.

About 500 people spent the night outside St Paul's Cathedral in London's financial district where around 70 tents could be seen. Some 200 people also camped in front of the European Central Bank building in Frankfurt and 50 tents were seen outside the stock exchange in Amsterdam.

Tens of thousands of people rallied in more than 1,500 cities in more than 80 countries and regions on Saturday, a "Day of Rage" against bankers and politicians.

The demonstrations coincided with the G20 meeting in Paris, where finance ministers and central bankers from major economies were holding talks on the debt and deficit crises afflicting many Western countries.

The Occupy Wall Street movement has gathered steam over the last month, culminating with the global day of action.

The Rome event drew tens of thousands of people and snaked through the city center.

Hundreds of hooded, masked demonstrators rampaged in some of the worst violence seen in the Italian capital in years, setting cars ablaze, breaking bank and shop windows and destroying traffic lights and signposts.

Police fired volleys of tear gas and used water cannon to try to disperse militant protesters who were hurling rocks, bottles and fireworks, but clashes went on into the evening.

Smoke bombs set off by protesters cast a pall over a sea of red flags and banners bearing slogans denouncing economic policies the protesters say are hurting the poor.

Protesters in the US are angry that banks are enjoying booming profits after getting massive bailouts in 2008 while average people are struggling in a tough economy with more than 9 percent unemployment and little help from Washington.

In New York, where the movement began when protesters setup a makeshift camp in Lower Manhattan on Sept 17, organizers said the protest grew to at least 5,000 people as they marched to Times Square in midtown Manhattan.

A few dozen were arrested for minor offences.

Small and peaceful rallies got the ball rolling across the Asia-Pacific region on Saturday. In Auckland, New Zealand's biggest city, 3,000 people chanted and banged drums.

In Sydney, about 2,000 people, including representatives of Aboriginal groups and trade unionists, protested outside the central Reserve Bank of Australia.

Hundreds marched in Tokyo. Many gathered to complain about radiation leaks from the Fukushima nuclear power plant, seven months after an earthquake and tsunami.

In Hong Kong, home to the Asian headquarters of investment banks including Goldman Sachs, over 100 people gathered at Exchange Square in the Central district. Students joined with retirees, holding banners that called banks a cancer.

Portugal was the scene of the biggest reported protest action, with more than 20,000 marching in Lisbon and a similar number in the country's second city Oporto, two days after the government announced a new batch of austerity measures.

Hundreds broke through a police cordon around the parliament in Lisbon to occupy its broad marble staircase.

"This debt is not ours!" and "IMF, get out of here now" demonstrators chanted. Banners read: "We are not merchandise in bankers' hands!" or "No more rescue loans for banks!"

Around 4,000 Greeks with banners bearing slogans like "Greece is not for sale" staged an anti-austerity rally in Athens' Syntagma Square, the scene of violent clashes between riot police and stone-throwing youths in June.

Many were furious at how austerity imposed by the government to reduce debt incurred by profligate spending and corruption had undermined the lives of ordinary Greeks.

In Paris, around 1,000 protesters rallied in front of city hall, coinciding with the G20 finance chiefs' meeting, after coming in from the working class neighborhood of Belleville where drummers, trumpeters and a tuba revved up the crowd.

The global protests were a response to calls by New York demonstrators for others to join them. Their example has prompted similar occupations in dozens of US cities.

Hundreds turned out in Washington DC, while a protest in Los Angeles drew about 5,000 people.

"I am going to start my life as an adult in debt and that's not fair," student Nathaniel Brown said in Washington.

"Millions of teenagers across the country are going to start their future in debt, while all of these corporations are getting money fed to them all the time and none of us can get any."

In Madrid, around 2,000 people gathered for a march to the central Puerta del Sol. Placards read: "Put the bankers on the bench" and "Enough painkillers - euthanasia for the banks."

"It's not fair that they take your house away from you if you can't pay your mortgage, but give billions to the banks for unclear reasons," said 44-year-old telecom company employee Fabia, who declined to give her surname.

AFP contributed to this story.