Violence broke out in Portland, Oregon, as groups of demonstrators both supporting and opposing President Trump converged downtown Sunday amid escalating tensions.

Police said people hurled bricks and at least one gas bottle at officers in Chapman Square. Law enforcement fired back with "less-lethal chemical munitions," according to police.

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Officers arrested at least 14 people and confiscated various weapons, including what appeared to be a knife, brass knuckles and a homemade slingshot. They also had to dodge balloons filled with a foul-smelling liquid, Fox 12 reported.

In addition, officers detained a large crowd several blocks north of the pro-Trump rally. Several journalists at the scene said they were blocked in, along with demonstrators, and were told by officers that they were detained pending investigation for disorderly conduct. A Portland Tribune reporter tweeted that she was held but eventually released after police took photos of her ID.

Crowds at the demonstrations swelled to several thousand. Much of the city has been on edge after the deadly stabbing of two men who tried to stop another man's anti-Muslim tirade just over a week ago.

Last week Mayor Ted Wheeler unsuccessfully tried to have the permit for the pro-Trump revoked, saying it could further enflame tensions. Federal officials said there was "no basis" to revoke the permit on federal land, Fox 12 added.

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The free-speech rally organized by a conservative group called Patriot Prayer drew hundreds to a plaza near City Hall. Rally organizer Joey Gibson told the crowd that the goal was to wake up the liberty movement. "It's OK to be a conservative in Portland," he said.

Demonstrators chanted "USA" and held supportive banners.

The group was met by hundreds of counter-protesters organized by immigrant-rights, religious and labor groups. Many of them filled the steps of City Hall, drummed and played music and held signs, some of which read "Our city is greater than hate" and "Black lives matter." Some chanted "love, not hate" and "Go home, fascists."

"We build our hope and our stamina for justice by showing up," the Rev. Diane Dulin of the United Church of Christ said in a statement ahead of the rally.

The suspect in the light-rail stabbings, Jeremy Joseph Christian, 35, attended a similar rally in late April wearing an American flag around his neck and carrying a baseball bat. Police confiscated the bat, and he was then caught on camera clashing with counter-protesters.

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On May 26, Christian killed two men and injured another on the light-rail train when they tried to help after he verbally abused two young women, one wearing a hijab, investigators said. Christian has been charged with aggravated murder and other counts.

In a video posted on Facebook, Joey Gibson of the group Patriot Prayer condemned Christian and acknowledged that some rallies have attracted "legitimate Nazis." He described Christian as "all crazy" and "not a good guy."

Mat dos Santos, the legal director for the American Civil Liberties Union of Oregon, has said it was wrong and unconstitutional for Wheeler to try to stop the demonstrations based on the viewpoint of the organizers.

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The Associated Press contributed to this report.