SEATTLE - Police arrested 17 people suspected of assault and property damage Wednesday night when a May Day demonstration turned violent and marchers broke windows and pelted officers with rocks, bottles and fireworks.
Eight officers suffered minor injuries clashing in the streets, police said.
The "anti-capitalism" protest followed a peaceful immigration reform march and rally earlier in the day. It was the second year in a row for May Day violence in the Emerald City.
Police had said 18 people were arrested but revised the number to 17.
Officers used "flash bangs" and pepper spray against dozens of protesters who threw construction street barriers, trash cans and newspaper bins on the streets in an attempt to block advancing police officers. Windows of local businesses were broken and vehicles with people in them were banged around.
"We're a bigger and better city than this. I look at this and I am disappointed that this is the picture the world sees of us," Seattle Mayor Mike McGinn said late Wednesday.
Police used their bikes to shield businesses and eventually began to use "flash bang" grenades - releasing a flash of light, smoke and a loud noise - to disperse the crowd. But that pushed the group to the Capitol Hill neighborhood, and they left a wake of overturned trash cans and debris on the street, as well as smashed windows on local businesses.
There were no immediate cost estimates from damage.
The injured officers suffered mostly scrapes and bruises, said Police Capt. Chris Fowler. One officer was hit by a rock on her knee.
Initially, the protesters concentrated on a business sector of downtown Seattle. Despite lacking a permit to march, Seattle police escorted them.