Angry protesters in Brighton ripped up a United States flag to vent their bile at the start of war with Iraq.

Hundreds of demonstrators, many of them children, stormed the American Express building yesterday.

Police prevented the crowd entering the offices but three flag poles were brought crashing to the ground.

Employees told of their disgust as someone within the throng shredded the Stars and Stripes.

Police confirmed three people were arrested during yesterday afternoon's demonstrations for public order offences and criminal damage.

One Amex employee said: "I have just witnessed one of the most disgusting and ignorant scenes of my life.

"A crowd of about 100 people had gathered on the steps and seemed to be trying to force their way into the building, unsuccessfully.

"That was until they spotted the three flag poles that stand next to the building sporting the British, European and American flags. The crowd surged around these flags and brought them to the ground.

"All three flags were removed and, to the background of cheering, the American flag was torn into pieces. My heart sank and I wanted nothing more than to tear into the crowd and teach them a lesson in what the war was really about."

The employee described their behaviour as "absolutely, disgustingly, sickening".

A colleague described "scenes of mayhem" as upwards of 300 protesters tried to force their way into the building.

Superintendent Peter Coll, of Brighton police, said: "Someone grabbed hold of the US flag from the American Express building and they were attempting to burn it.

"It did not burn and they were slashing it with a knife. We arrested the person for criminal damage.

"We have tried to allow and facilitate protests as far as possible. We have had hundreds of people demonstrating and if we arrested everyone who sat in front of cars, we would have ground to a halt. It would also affect the mood of the crowd.

We have had to find a sensible balance. My priority all afternoon was to prevent violence and damage.

"If there are further protests, I would appeal to people's better nature to say please don't damage property or use violence.

"Make your protests but realise when you stop traffic, it massively winds up people who might otherwise support the protest."

A spokeswoman for Amex would not comment on the protest but said any employees shaken by the scenes would be able to talk with their managers.