Protesters are demonstrating in Portland, Oregon to support a movement against racial injustice.
They have been gathering despite pushback from law enforcement agents set to maintain "law and order" by the US federal government.
Local authorities have denounced the federal militarised agents, stating that the law enforcement effort is making the situation worse.
Law enforcement officials appeared to fire tear gas on protesters Monday to disperse them, AP reported.
Clashes between police and protesters have often broken out during the nightly protests.
The demonstrations in front of the city's federal courthouse are being held over the killing of George Floyd in Minneapolis.
Floyd's death in police custody sparked protests throughout the United States over racial injustice.