(CNN) - Mayor Ted Wheeler was tear gassed in downtown Portland early Thursday morning, according to video and posts on Twitter from a New York Times journalist.

"It stings. It's hard to breathe. I can tell you with 100% honesty I saw nothing that provoked this response," Wheeler said to the Times camera. "I'm not afraid but I am pissed off."

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Wheeler addressed the presence of federal officers in his city who have been deployed by the Trump administration and are heavily opposed by local leaders across the state and nation. The President said the effort was to protect federal property, but protesters say the action itself has fueled the public's outrage. Demonstrations in the city, many of which have been peaceful, have been ongoing for more than 50 days.

"It is an unconstitutional occupation. The tactics that have been used by our federal officers are abhorrent. They did not act with probable cause, people are not being told, who they are being arrested by, and you're been denied basic constitutional rights," the mayor told the crowd.