The protests took place at several downtown locations, with reported brief clashes between demonstrators and police, witnesses said.

The main group of protesters carried signs, shouted slogans and blasted music as they roamed the Financial District. Some threw play money in the air and waved pink flags.

About 150 people were arrested by mid-afternoon as police tried to clear some locations of the protesters, according to the San Francisco Chronicle newspaper.

One scuffle took place after about two dozen demonstrators staged a "die-in" in the intersection of Market and New Montgomery streets about 12:15 p.m. and were surrounded by 80 police officers in riot gear.

After more than two hours of protests -- and about 100 arrests -- authorities finally cleared the intersection and reopened Market Street to traffic at 2:30 p.m.

As protesters were arrested, more demonstrators from the scores who were watching from the sidewalk rushed to fill their place. Among those taken away were 20 people, calling themselves Act Against Torture, who were wearing orange jumpsuits with black hoods over their heads, said the report.

"We're here to get arrested," said Leslie Mullin, 63. "The people have to step into this war because none of the government officials want to do it for us. We've gone all over town and people are saying, 'Good for you.' "

Left-wing activist Daniel Ellsberg told the crowd, "The symbolism of people lying in death appears to symbolize the life and death seriousness as we enter the sixth year of this crime against the American people." He soon sat down in the street and was himself arrested.

No injuries were reported in the protests, which began around 8a.m.

Across the bay in Berkeley, about 100 demonstrators gathered at the Martin Luther King Jr. Civic Center Park at noon to hear peace activist Cindy Sheehan speak. About 80 people marched afterward to the Marine Corps recruiting station on Shattuck Square, where demonstrators had gathered earlier, said the report.

After a short rally at the recruiting station -- which has been the focus of a weeks-long protest mounted by the anti-war group Code Pink, a group of protesters marched to the campus of the University of California in Berkeley, according to the report.

Organizers said they have planned a larger-scale march from Civic Center to the Mission District, beginning from 5 p.m.