Masked protesters ransacked Brighton Town Hall yesterday in the name of peace.

A group of about eight hardline activitists broke away from a 5,000-strong demo in the city centre and went on the rampage in the historic building.

The marriage room was trashed. Furniture was wrecked and floral decorations destroyed.

Fittings in the main lobby were smashed up.

Microphones in the council chamber, worth £2,000 each, were ripped out and bent.

Anti-war graffiti was scrawled on walls. Windows were broken and computers smashed up.

The bust of Somers Clarke, which has stood outside the main committee room for more than a century, was knocked off its pedestal and split into two.

Police at first took a relaxed attitude to yesterday's series of protests and marches which gradually brought city traffic to a standstill from noon.

More than 150 officers were deployed to marshall the demonstrators who flocked to Churchill Square following the outbreak of war with Iraq.

But as evening fell the sit-down demo, which sprawled from the shopping centre down to the clock tower, splintered into groups with some intent on causing mayhem.

One officer was hit with a bottle and others had bleach thrown at them.

Seven people were arrested for burglary, criminal damage and assault. Three remained in custody today over the Town Hall invasion.

Senior officers, who had ordered low-key policing to allow people to voice their views, today took the decision to move up a gear in the wake of last night's violence.

Chief Superintendent Paul Curtis, Brighton and Hove police commander, said: "We allowed a peaceful protest to take place and we will continue to allow such demonstrations as far as possible.

"However, we will not tolerate the small core of people who attend the demonstrations purely to use violence and cause criminal damage.

"Officers will take robust action should this happen and resources are in place to ensure the public is kept safe."

Town Hall staff worked through the night to clear the mess to enable four weddings to take place today.

Owen Goodey, facilities officer, surveyed the scene and said: "It was supposed to be in the name of peace and yet they have done all this."

Brighton and Hove City Council has only made one statement about the war against Iraq.

It passed a resolution opposing any military action without the backing of the United Nations.

City council leader Ken Bodfish said: "I deplore this violent and mindless attack on public property.

"One wonders what kind of person thinks that wrecking people's wedding ceremonies has any place in legitimate protest."

Opposition Tory leader Brian Oxley said: "I'm extremely concerned about what happened last night and that once again local people are going to have to foot a large bill to deal with damage.

"I did ask a question about the security of buildings in January."

Chief Supt Curtis added: "We are anticipating further demonstrations and again will facilitate those whilst they are peaceful and lawful.

"We want to stress that the safety of the people who live, work and visit the city is paramount and police will do everything they can to ensure the protests do not become riots.

"We are not prepared to accept the scenes of yesterday."