After several quiet nights of protests in Portland, hundreds of demonstrators erected barricades outside the Portland Police Bureau's North Precinct along Northeast Martin Luther King Boulevard on Thursday night.

Police responded with forceful crowd control tactics to clear the street, including deploying tear gas and flash-bangs. Videos by freelance reporters and activists show protesters then set the barricades on fire and smashed the windows of nearby stores, including a Bank of America branch.

Police said this morning that protesters had set the North Precinct station on fire, although that assertion could not be independently corroborated. A police statement said officers and others—presumably under arrest—were inside the precinct building at the time it was set on fire, but a representative did not immediately respond to follow-up questions about whether anyone was evacuated.

The barricades appear to be the latest attempt to create a permanent protest zone in Portland, like the Capitol Hill Occupied Protest in Seattle. For many nights over the past two weeks, small groups of protesters have tried to block off streets, although the efforts rarely appeared as ambitious as last night's attempt.

Starting at about 11 pm, protesters formed barricades around the precinct using vehicles, wooden pallets and dumpsters. Police say the demonstrators attempted to break into the building but were unsuccessful. They proceeded to board up and tag much of the building.

Around 1 am, police declared an unlawful assembly—typically a signal that they intend to clear the streets. PPB officers fired tear gas, flash-bangs and rubber bullets at the crowd, according to accounts on Twitter.

Police say that around 2:15 am, demonstrators set fire to a portion of the precinct. Police say demonstrators broke into, looted and set fire to nearby businesses at about 3 am. Video showed the Bank of America branch on Northeast Martin Luther King, Jr. Boulevard with its window shattered. Someone tagged the building: "Protests are effective when they are expensive."

At about 2 am, medics treated protesters who were injured by the police's use of weapons, according to reporter Tuck Woodstock. It is unclear how many protesters were injured.

By 3:30 am, most protesters had gone home. The bureau arrested four demonstrators over the course of the night.

Activists on social media declared the standoff a triumph. But it also appears to be the first time in weeks, since the beginning of protests in late May, that hostilities between protesters and police moved into neighborhoods on the east side of the Willamette River, instead of remaining concentrated in downtown. That could be a delicate moment, given that demonstrations are decreasing in size but not in fury.