By Deborah Bloom

PORTLAND, Ore. (Reuters) – Protests flared again in Portland overnight on Monday as demonstrators clashed with police on the streets of the city which after months of sometimes violent confrontations has become a focal point of the U.S. presidential race.

Police used smoke grenades and pepper balls to control the crowd of protesters. Police acknowledged in a statement that officers “deployed some crowd control munitions” and said 19 people were arrested, mostly on charges of disorderly conduct and interfering with police.

About 200-300 people gathered in the downtown area to march to the apartment of Portland Mayor Ted Wheeler to demand his resignation. They were seen setting fire to wooden benches and plastic trash bins along the march.

Police declared the gathering unlawful and later upgraded it to a riot after protesters set fire in an apartment building. The area was secured to allow firefighters to respond to the situation, police said.

Portland has seen nightly protests since the killing of George Floyd, a 46-year-old Black man, in Minneapolis on May 25. Hundreds of demonstrators have been arrested since the protests began.

In recent weeks, tensions between right- and left-wing groups in the city have roiled downtown.

Supporters of U.S. President Donald Trump have converged on the city as counter demonstrators, including one man who was fatally shot on Saturday night. Nobody has been charged in that case as police review poor-quality video of the incident.

State police and officers from neighboring suburbs were sent to Portland on Monday following the shooting.

(Additional reporting by Ann Maria Shibu in Bengaluru; writing by Kanishka Singh, editing by Angus MacSwan and Chizu Nomiyama)