Police opened fire with nonlethal projectiles during an antiwar protest at the Port of Oakland today, injuring at least six demonstrators and six longshoremen standing nearby.

Most of the 500 demonstrators at the port were dispersed peacefully, but at two gates, police said, officers opened fire when protesters refused to move and some demonstrators threw rocks and bolts. The longshoremen, pinned against a fence, were caught in the line of fire.

Demonstrators said they targeted the port because at least one company there is handling war supplies. They said it was the first time they had been fired upon in Bay area protests since the Iraq war began last month.

"Oakland police are being the most aggressive of any department I've seen in the Bay area since the war began," said protester Damien McAnany, a database manager. "The San Francisco Police Department never used any of this stuff against us."

Oakland Police said at least 24 people were arrested.

"Some people were blocking port property, and the port authorities asked us to move them off," said Deputy Police Chief Patrick Haw. "Police moved aggressively against crowds because some people threw rocks and big iron bolts at officers."

Police spokeswoman Danielle Ashford said officers fired bean-bag rounds and wooden dowels. They also used "sting balls," which send out a spray of BB-sized rubber pellets and a cloud of tear gas.

"When they hit you, it feels like a bee sting," Haw said.

Six longshoremen were treated by paramedics, as were at least six protesters. Injuries included bruises and welts.

"I was standing as far back as I could," said longshoremen Kevin Wilson. "It was very scary."

A "sting ball" grenade thrown by police explodes over protesters during an antiwar demonstration in Oakland, Calif. Police said 24 people were arrested.