Updated

Police fired pepper spray and arrested a half dozen people Thursday night as anti-capitalist marchers meandered through Seattle, hours after hundreds of peaceful demonstrators took part in a May Day march in support of immigrant rights and a boost in the minimum wage.

Police said they used pepper spray after some marchers threw bottles at officers in downtown Seattle. Protesters later started trash can fires in the Capitol Hill neighborhood. Another arrest came after a brick was hurled at officers. A gun was recovered from one of those arrested, police said.

By late Thursday night, the anti-capitalist protesters had marched in a rambling circuit from Capitol Hill to downtown Seattle and back again before police hemmed them in. Some tossed firecrackers at police, officers said.

All through the day and night, Seattle police were out in force on bicycles, foot and horseback. They supplemented their numbers with officers from several other jurisdictions.

Violence has plagued May Day in Seattle during the past two years, with protesters challenging police in the streets and sometimes stealing the thunder of much larger daytime events.

Last year, police arrested 18 people from a crowd that pelted them with rocks and bottles.

Seattle police noted a marked uptick in anti-authority rhetoric leading up to this year's May Day events, said Capt. Chris Fowler, in charge of the department's response to the demonstrations.

Police escorted both the permitted march of immigration and labor activists and later, unpermitted marches, allowing them to block traffic but prepared to step in to stop property damage.

Businesses downtown also prepared, posting security guards outside, taping paper over their windows to discourage graffiti, and using metal coat hangers to tie down iron grates along the sidewalks.

The earlier boisterous May Day rally started in south Seattle and headed to Westlake Park downtown, with demonstrators waving red signs seeking an end to deportations and "poverty wages" and calling for a $15-an-hour minimum wage.

Earlier Thursday, Mayor Ed Murray announced a plan to phase in a $15 minimum wage in the city over the next seven years.

Daniel Stender, 26, was at the rally holding a sign pushing for quicker action on getting to a $15 minimum wage.

"It's getting ridiculous. It's getting to the point where you can't afford things," he said.

The police department's blog said vandals spray-painted a few businesses early Thursday in the Capitol Hill neighborhood — a car dealership, bank, restaurant and "the neighborhood headquarters of the oppressive regime at the United States Postal Service."

Officers also found "Kill SPD" painted on the bank, and a flier was circulated calling for killing officers.