The mayor of the U.S. city of Portland, Ted Wheeler, was stung by tear gas early on Thursday morning after he joined demonstrators protesting against racial injustice and police brutality.

Security forces have frequently tear-gassed and clubbed demonstrators during weeks of unrest and Wheeler, visiting the protest site outside the federal courthouse in downtown Portland, urged federal agents to be withdrawn from the city.

“They’re not wanted here,” he said.

But Wheeler, who is also the city’s police commissioner, was jeered at by demonstrators who called on him to resign and chanted “Shame on You”. Some said he should have done more to protect Portland’s citizens.

The deployment of federal agents in Portland on July 4 is a flashpoint in a national debate over civil liberties that has roiled the United States since the death of George Floyd in police custody in Minneapolis on May 25.

Demonstrators and local officials see the move as a political ploy by U.S. President Donald Trump, a Republican, to drum up a “law and order” campaign as he faces an uphill re-election battle.

Wheeler, a Democrat, has called the intervention an abuse of federal power and said it was escalating the violence. Wednesday saw bigger and bigger crowds of supporters joining the demonstrations.

After a few demonstrators had set trash bags on the fire outside the courthouse, federal agents inside the Justice Center fired tear gas, flash bangs and pepper balls into the area.

Wheeler stood at the front of the line, in a surgical mask and goggles, and began to cough, a Reuters reporter said. He experienced two rounds of heavy tear gas. His eyes and nose were running, his face was red and his eyes were bloodshot.