RTD closed Union Station and suspended public transit in the area because of safety concerns and in coordination with Denver police, a spokesperson said.

Denver police arrested 18 individuals during an "ICE Out!" immigration protest, with tensions over ICE policies sparking demonstrations and officials responding to potential conflict.

Protesters clashed with police in Denver at West Colfax and Osage Street. Police said protesters were trying to get to the highway.

Denver police arrested 17 protesters on suspicion of graffiti, interference with law enforcement, obstructing streets, throwing objects and assault, according to the police department.

At least 1,500 "No Kings" protests nationwide started Saturday on the same day President Donald Trump scheduled a large-scale military parade in Washington, D.C. on Flag Day and his 79th birthday.