The tense standoff between demonstrators and federal police dispatched to Portland, Oregon, dragged on Thursday after the city's mayor was tear-gassed by U.S. government agents as he made an appearance outside a federal courthouse during raucous protests.

Mayor Ted Wheeler and hundreds of others Wednesday night were objecting to the presence of federal police sent by President Donald Trump, who labeled the demonstrators as "agitators & anarchists" after Wheeler was gassed. 

Two government watchdogs said Thursday that they had opened investigations into the conduct of federal agents responding to unrest in Portland, Oregon, following abuse of power allegations by members of Congress, local officials and the public.

The Justice Department watchdog said that it would investigate use of force allegations in Portland, while its counterpart at the Department of Homeland Security said it would examine whether officers from the agency improperly detained and transported protesters in the city last week.