Click photo to enlarge
Protesters link arms on the floor of the Obama campaign headquarters building in downtown Oakland.

OAKLAND -- A protest at the Barack Obama campaign headquarters in downtown Oakland ended peacefully late Thursday, with a handful of arrests but no reports of violence.

At least 60 protesters rallied at the building at 17th Street and Telegraph Avenue around 5:30 p.m., when police were summoned to guard all entrances. But seven protesters found their way inside the building, linked arms and refused to leave, police said.

Officers unsuccessfully negotiated with the group for several hours to leave the building, but they remained there until 9:12 p.m., when one of them voluntarily decided to leave. The remaining six were arrested for trespassing, police said.

Police secured the building and the remaining protesters outside dispersed peacefully. Police did not use force and there were no reported injuries to the protesters or officers.

Organizers of the protest said it was to demand justice for Bradley Manning, the Army private accused of leaking state secrets to WikiLeaks. The 24-year-old Manning has been indicted on 22 counts of providing sensitive information to the website.

Organizers said similar protests took place in Seattle, Tacoma and Portland.

The Obama headquarters building in Oakland had previously been targeted by protesters, who broke a window there earlier this month during a march after the city refused to grant a permit to allow a demonstration at the city's First Friday event in downtown.

Reach Kristin J. Bender at kbender@bayareanewsgroup.com. Follow her at Twitter.com/kjbender.