400 arrests in Occupy protest

More than 400 people were arrested during a chaotic day of Occupy protests in the US city of Oakland that saw demonstrators break into city hall and burn an American flag and police fire tear gas, and use flash grenades to disperse the crowds.

It was the most turbulent day of protests since November, when Oakland police forcefully dismantled an Occupy encampment.

Authorities say protesters clashed with police throughout the day, at times throwing rocks, bottles and other objects at officers.