Richmond police arrested six men for unlawful assembly Saturday night into Sunday morning after hours of violent protests in which fires were set and windows broken and officers were assaulted with batteries, rocks, water bottles and other objects.

Mayor Levar Stoney (D) and Police Chief Gerald Smith said in a news conference Sunday afternoon that white supremacists, antifa activists and “boogaloo boys,” a far-right anti-government extremist movement, staged or participated in the demonstrations. Black Lives Matter activists did not join them, Stoney said.

Smith said the six men were charged with unlawful assembly. The Richmond Times-Dispatch reported the men are between the ages of 26 and 36, and one was also charged with assaulting a law enforcement officer and rioting. Smith said they already had in custody people who are accused of damaging property; they also could face charges.

A Richmond police spokesman could not be reached for comment.

The police declared the event unlawful about 11 p.m. Saturday, after officers were hit with projectiles outside their headquarters, according to the agency’s Twitter feed. Police used chemical agents to disperse the crowd.

The violence ends the city’s streak of nonviolent protests in recent weeks, Stoney and Smith said, as they blamed the demonstration on outsiders.

Richmond has seen protests on an almost nightly basis since late May, many of them centered around issues of racial justice and police brutality, and demands that the city remove statues honoring the Confederacy.

Former police chief William Smith resigned in mid-June after two nights of tense demonstrations that involved chemical gas and rubber bullets outside the city’s police headquarters.

The earlier protests also included some arrests. At one point, a police SUV drove through a crowd of protesters and bumped several people, although there were no serious injuries.