Officers opened fire to disperse a crowd of between 500 to 700 people picketing the docks of shippers American Presidents Lines at the port of Oakland in California as part of a nationwide civil disobedience campaign.

Six people were injured in the incident, intended to protest an alleged contract the shipping line has won from the US government to ship war supplies to US-led forces in Iraq.

"Demonstrators were picketing legally to protest the war when police overreacted and began pelting them with rubber bullets and other objects without warning," said Patrick Reinsborough of Direct Action to Stop the War.

Police said they had warned the protesters to clear the area around the port several times and that protesters had lobbed rocks and bolts at officers before authorities resorted to a barrage of non-lethal objects.

"Our intent out is to allow people to express their first amendment (freedom of expression) rights peacefully and within the law," Deputy Chief Patrick Haw said.

But demonstrators, who brandished placards bearing slogans that read "Shut down the war makers" and "Embargo war cargo" accused the officers of using excessive force.

"These are peaceful protesters being shot at by police," said demonstrator Bradley Angel.

The protest was part of a rash of similar demonstrations and acts of civil disobedience aimed at opposing the invasion of Iraq.

Protesters had also gathered outside government offices in nearby San Francisco to denounce the US action, while similar demonstrations were planned for New York and Washington.

SPACE.WIRE