Police were out in force for the G20 summit Thursday, swarming the east London riverside site as small groups of demonstrators protested world poverty and climate change.

Officials also raided addresses they believe are linked to protesters involved in some of the more violent demonstrations Wednesday. Police visited two London squats in which they believe the organizers were living, Sky News reported.

A French daredevil scaled a London insurance building to unfurl a banner, delighting people on the ground.

At the ExCel Center in the Docklands area, where leaders of the Group of 20 financial powers held talks on the global economy, police manned barriers and checkpoints around the security perimeter, turning away anyone without accreditation within a half-mile radius. Police boats patrolled the River Thames.

Outside the summit venue, dozens demonstrated with signs that read "Stop Ethiopia from Starving." Other protesters sat and played a giant Monopoly game near the London Stock Exchange.

Click to view protest photos.

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"The question is of course who has got the monopoly? It is fairly obvious the G20 are the global financial elite," said Clare Smith, 27, one of the protesters.

"Meanwhile the poor are getting poorer and that has even started to show in this country, but has obviously been going on across the world for some time," she said.

Stop the War coalition supporters also gathered outside the Docklands venue by the Thames.

"I'm here because part of the world's economic troubles can be helped if, instead of spending billions on weapons, we used it to help the poor," said Hazel Barkham, a hospital chaplain.

About 100 people demonstrated Thursday in the financial district, where French daredevil Alain Robert scaled Lloyds of London's high-rise headquarters as office workers gathered below to snap photos.

Robert, dubbed the French spider-man, has scaled dozens of tall structures around the world without ropes or harnesses as part of a campaign to draw attention to global warming. He unfurled another climate change banner in his climb Thursday, before later being led away by police.

About 100 more people demonstrated near London Bridge.

Police said there had been about 100 arrests so far, most of them Wednesday.

A day earlier, some 4,000 anarchists, anti-capitalists, environmentalists and others had streamed into central London near the Bank of England for largely peaceful protests. Still, some protesters broke into the Royal Bank of Scotland building and vandalized the Bank of England building.

Tens of thousands of demonstrators, meanwhile, were descending on two southwest German towns and the French city of Strasbourg on Thursday to protest a cross-border NATO summit marking the alliance's 60th anniversary.

President Barack Obama, German Chancellor Angela Merkel and French President Nicholas Sarkozy are among 28 world leaders expected to be on hand for the two-day summit beginning Friday after the end of London's G20 summit.

Click here to read more on this story from Sky News.

The Associated Press contributed to this report.