Several members of the far-left group were seen trying to grab “Make America Great Again” hats off the heads of supporters of President Trump, the Washington Times reported.
Members of Black Lives Matter D.C. also attended, the Washington Post reported.
A “massive” group of District of Columbia police officers was assigned to the rally in an effort to prevent violence, according to the Post.
Police had broken up at least one direct clash between the conservative Proud Boys group and members of Antifa, according to the Post. Afterward, police worked to keep the two sides apart, the report said.
Antifa members were seen dragging objects into the street to impede traffic in the rally area, the Times reported.
No arrests were made, District police Chief Peter Newsham told the newspaper.
According to the Post, authorities in the nation’s capital wanted to avoid a situation similar to last month’s violence in Portland, Ore., that prompted that city’s police to use tear gas against demonstrators.
Conservative writer Andy Ngo posted photos of his injuries after he was attacked in Portland.
On Wednesday, former New York City police Commissioner Bernard Kerik told Fox News that he believes Antifa should be declared a domestic terror organization.
“This is an extremely violent group that goes out, threatens, intimidates, attacks with extreme violence for political reasons,” Kerik said on Fox News’ “Tucker Carlson Tonight.”
Conservative speakers addressing Saturday’s free-speech gathering in D.C. included Proud Boys founder Gavin McInnes and writers Laura Loomer and Milo Yiannopolous, according to the Post.
Several speakers complained that they had been banned from social media because of their conservative views, the Daily Beast reported.
“I may have been the first person in history completely banned from Tinder,” speaker Greg Aselbekian shouted, according to the outlet.
Previous “Demand Free Speech” events were held in New York and San Francisco, the Post reported.
Fox News' Danielle Wallace contributed to this story.