An empty tear gas canister lies in the street.

Protesters link arms and chant in a confrontation with police in front of Oakland City Hall.

A cloud of tear gas engulfs a protester.

A passing motorist gives a fist bump to a protester marching down 20th Street in Oakland.

Don Reniff and Chelsea Lohr kiss during the march.

Protesters, covering their mouths to avoid inhaling tear gas, help a woman in a wheelchair.

A man watches out of the window of a bus on 20th Street as a large group of protesters pass by.

A bicyclist ducks to avoid being shot with pepper-spray projectiles after the police line at 17th and Broadway fired tear gas at protesters.

Svend Larose covers his mouth but holds his ground after being tear-gassed by police.

Protesters threw dollar bills at police, asking "Will you protect us now?"

Tear gas smoke billows out of a canister on Broadway in downtown Oakland.

The epicenter of the protest movement against economic injustice shifted west on Tuesday, with police and demonstrators clashing at Occupy Oakland. The confrontation began in the wee hours of the morning, when police swept in to evict protesters from the camp they'd occupied for two weeks on the plaza outside Oakland City Hall. Last night, several hundred activists regrouped for a march to retake what many of them call Oscar Grant Plaza—a reference to an unarmed man killed by local transit police in 2009.

Over the course of the evening, police in riot gear fired tear gas and pepper balls into the crowd at least five times, sending people running for cover. More than 100 demonstrators were arrested, and Occupy Oakland organizers pledged another protest for Wednesday night to continue the effort to move back onto the plaza.