More than 250,000 people took to London's streets to protest the toughest spending cuts since World War II _ one of the largest demonstrations since the Iraq war _ as riot police clashed with a small groups. More than 200 people were arrested.

Although most of Saturday's demonstration was peaceful, clashes continued into the night as dozens of protesters pelted officers with bottles and amonia-filled lightbulbs. Groups set several fires and smashed shop windows near tourist landmarks such as Trafalgar Square.

Teachers, nurses, firefighters, public sector workers, students, pensioners and campaign groups all took part in Saturday's mass demonstration.

"They shouldn't be taking money from public services. What have we done to deserve this?" said Alison Foster, a 53-year-old school teacher. "Yes, they are making vicious cuts. That's why I'm marching, to let them know this is wrong."

Britain is facing 80 billion pounds ($130 billion) of public spending cuts from Prime Minister David Cameron's coalition government as it struggles to slash the country's deficit. The government has already raised sales tax, but Britons are bracing for big cuts to public spending that are expected next month.

Treasury chief George Osborne has staked the government's future on tough economic remedies after Britain spent billions bailing out banks. Some half a million public sector jobs will likely be lost, about 18 billion ($28.5 billion) axed from welfare payments and the pension age raised to 66 by 2020.

Commander Bob Broadhurst of the Metropolitan Police confirmed more than 250,000 people had marched peacefully, but said around 500 caused trouble.

Hundreds were arrested and police expected that number to rise. Dozens were injured, and several were admitted to hospitals for a range of problems, including shortness of breath and broken bones. Five police officers were also injured.

The demonstration began in the afternoon. Police said one small group of protesters broke away from the main march, scuffling with police officers and attempting to smash windows on two of London's main shopping streets. Others threw objects at the posh Ritz Hotel in nearby Piccadilly.

The protesters, shouting "Welfare not Warfare!" outnumbered the police. Some attacked police officers with large pieces of wood. A handful of bank branches were damaged when groups threw paint and flares at buildings.

Still, the day's protest otherwise had a carnival feel with music, big screen TVs and performers in Hyde Park, one of London's biggest public gardens.

The TUC, the main umbrella body for British unions, says it believes the cuts will threaten the country's economic recovery, and has urged the government to create new taxes for banks and to close loopholes that allow some companies to pay less tax.

TUC general secretary Brendan Barber said he regretted the sporadic violence.

"I don't think the activities of a few hundred people should take the focus away from the hundreds of thousands of people who have sent a powerful message to the government today," he said. "Ministers should now seriously reconsider their whole strategy after today's demonstration. This has been Middle Britain speaking."

Ed Miliband, leader of the opposition Labour Party, likened the march to the suffragette movement in Britain and the civil rights movement in America. "Our causes may be different but we come together to realize our voice."