Protesters gather in London's financial district on Wednesday ahead of the G20 summit. ((Tom Parry/CBC))

A man has been found dead at the G20 protest in England as thousands of protesters rallied ahead of the economic summit in London's financial district.

The man collapsed on the street near the Bank of England, London's Metropolitan police said.

Police did not give a possible cause of death.

Officials estimated that at least 4,000 people jammed into the area, with some chanting "Abolish Money" as they marched down the clogged streets.

Meanwhile, climate change activists pitched tents and organized sit-ins in front of buildings and anti-war campaigners held other rallies. Photos from the protests showed some demonstrators with bloodied faces and police said several officers were injured.

The demonstrators are vying for the attention of leaders of the G20 countries — including Prime Minister Stephen Harper and U.S. President Barack Obama — who are set to meet at one-day summit in London Thursday.

The leaders' main focus is expected to be the global economic downturn.

Hooded protesters march in London's financial district on Wednesday ahead of the G20 summit. ((Simon Dawson/Associated Press))

British Prime Minister Gordon Brown consulted with Obama ahead of the meeting and urged member countries to act with urgency to come up with a plan to combat the financial crisis. Other leaders are scheduled to attend a formal dinner on Wednesday night before participating in the Thursday meetings.

Police have closed off all roads leading into the financial district and aren't allowing any more demonstrators to enter or leave the area.

Leave for all city police officers has been cancelled and streets were lined with hundreds of officers. Most are carrying riot shields while others are on horseback.

A few of the protests turned violent — one band of demonstrators smashed windows of the Royal Bank of Scotland, scrawled the word "thieves" on the outside and stormed into the building. CBC London correspondent Ann MacMillan said some people were seen running from the bank carrying computers.

Rescued by the government in October, banks have become a lightning rod for public anger over banker excess blamed for the economic crisis.

Our streets, our banks, say protesters

Protesters hurled paint bombs and bottles, chanting: "These streets, our streets! These banks, our banks!"

A life-size mannequin in a bowler hat hangs from a stoplight in the street during protests in front of the Bank of England in London on Wednesday. A sign around its neck reads 'eat the bankers.' ((Tom Parry/CBC)) Some demonstrators have dubbed the summit protests as "Financial Fool's Day."

MacMillan described the mood at the rally as "very antagonistic."

Police officials reported that several officers had been injured during the rally, although they did say the mood had calmed later in the afternoon. At least 14 people were arrested in connection with the demonstrations.

Some police officers were pelted with eggs and fruit.

"There have been a number of missiles thrown at officers and a number of surges at the police cordons and increasing levels of violence towards police," a statement from police noted.

Images from the scene showed police waving batons, dispersing clouds of tear gas and pepper spray, with some protesters left with bloodied heads.

Officials said the security operation to contain the protest was one of the biggest in Britain's history and was aimed at protecting businesses, the Bank of England, the London Stock Exchange and other financial institutions in the city.

John Rees, the organizer of an anti-war protest, told CBC News the demonstration he was involved in was "entirely peaceful," as were the actions of most protesters.

"The media have been talking up some of the more violent elements in this and the police have been doing the same thing," he said.

"So I think that's regrettable, certainly but I do understand why people are very, very angry about these issues.

"There's a great deal of talk about a few windows going in today but there's a great deal more violence going on in the system when you think about the hundreds of people — thousands of people now — who have died in Afghanistan."

Bankers warned ahead of rally

Marina Pepper, a British activist who helped organize the protest, said the clashes with police escalated after the area was cordoned off.

"I think when people get frustrated and they're not allowed to go about their business … temperatures start to run high," Pepper said.

Police closed off the financial district as protests mounted on Wednesday. ((Tom Parry/CBC))

Demonstrators hoisted effigies of the "four horsemen of the apocalypse," earlier on Wednesday representing war, climate chaos, financial crimes and homelessness.

"Capitalism isn't in crisis — capitalism is the crisis," Pepper said. "The profits of a few people making lots of money is seen as more important than the needs of people all around the world."

Bankers were warned not to wear pinstripe suits on Wednesday and many opted for casual clothes or stayed home. But some financial workers taunted protesters from the upper level windows of buildings in the area and waved £10 notes at them.

"It seems like everything is in a mess," said protester Steve Johnson, 49, an unemployed construction worker. "You get bankers getting massive bonuses, and the MPs are lining their own pockets."