At least four people were stabbed near Harry’s Bar at 11th and F streets NW, a gathering point for the Proud Boys, a male-chauvinist organization with ties to white nationalism.

The victims were hospitalized and suffered possibly life-threatening injuries, D.C. fire spokesman Doug Buchanan said. It was not immediately clear with which groups the attackers or the injured might have been affiliated.

The violence escalated after an evening of faceoffs with counterprotesters that took place near Harry’s, Black Lives Matter Plaza, Franklin Square, and other spots around downtown.

At first, officers in riot gear successfully kept the two sides apart, even as the groups splintered and roamed. In helmets and bulletproof vests, Proud Boys marched through downtown in militarylike rows, shouting “move out” and “1776!” They became increasingly angry as they wove through streets and alleys, only to find police continuously blocking their course with lines of bikes.