(CNN) -- A May Day protest in downtown Seattle turned violent Wednesday night, with police saying they resorted to pepper spray to disperse demonstrators who pelted them with whatever was at hand.
Seattle Police said the crowd tossed rocks, bottles, metal pipes, fireworks -- and even a skateboard.
The clashes left eight officers with injuries, and police said they arrested 17 people, on various offenses including property destruction and assault.
The injured officers suffered mostly bumps and bruises with the exception. One officer, however, was struck in the knee by a fist-sized rock, Seattle Police said.
During the clashes, police deployed flash-bang grenades and tackled unruly protesters to the ground.
Other demonstrators ran through the fog created by tear gas wearing masks and holding protests signs.
A woman who was driving by the protest scene was wounded, slashed by glass, when a protester hurled a glass bottle at her car, shattering her window, police said. She was treated by a medic at the scene.
"Things have quieted down for the night. Officers will continue to patrol ," the department tweeted early Thursday morning.
The clashes came after a day of peaceful marches in the city, CNN affiliate KING reported.
Hundreds of thousands of people across the globe take to the streets on May 1 to demand better working conditions during what is known as International Workers' Day.
In Washington on Wednesday, two May Day groups, with differing views, fought in Lafayette Park near the White House, police said.
The skirmish, between a group calling itself the White Student Union and another, the May Day Workers, escalated as combatants threw bags of urine and flag poles at each other.
One person was arrested, U.S. Park Police said.
"We were here to protest communism and to stand up for the blue collar working class. And then I got urine thrown on me," said Matthew Heimbach, president of the White Student Union. "So it shows really how tolerant these people are."
John Zangas, who was with the May Day Workers, said people were offended by some of the statements from the White Student Union.
"I don't even want to characterize them but they're fairly bigoted," said Zangas.
CNN's Tina Burnside contributed to this report.