About 95 people were arrested and nine police officers were injured.

The Cenotaph and a statue of Winston Churchill were defaced with graffiti and a fast-food restaurant was ransacked.

Prime Minister Tony Blair has condemned the protesters as an "absolute disgrace".

"Their actions have nothing to do with conviction or belief and everything to do with mindless thuggery," he said.

The day, which marked the end of four days of May Day protest in the capital, had started peacefully.

Police looked on as demonstrators dug up clumps of turf in Parliament Square and planted seeds as part of their "guerrilla gardening" campaign to return parts of urban London to nature.

Barrage of bottles

About 1,000 people then headed off for Trafalgar Square. On the way a small group targeted a McDonald's restaurant in The Strand where one policeman was hit by a flying brick and every window in the burger bar was smashed.

Police cordoned off the area and then opened up a corridor to allow campaigners to leave. At that point, violence broke out again and police faced a barrage of bottles, sticks, iron bars and scaffolding.

Holiday leave for the capital's police officers had been cancelled to avoid a repeat of last year's violent demonstrations in the city's financial centre.

More than 5,000 officers from the Metropolitan Police, the City of London Police and the British Transport Police were on duty specifically to deal with the protests.

Operations were co-ordinated by Scotland Yard's control centre, where 100 officers monitored CCTV cameras and passed on intelligence to police on the ground.

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