In this file photo a peaceful crowd protest during a demonstration in front of the Multnomah County Justice Center in Portland, Oregon, on July 17, 2020. (ANKUR DHOLAKIA / AFP)

Unrest in Portland, Oregon, is taking on national political implications as United States President Donald Trump defends the actions of federal authorities against protesters in the city.

Trump condemned the Portland protests and violence in "Democratrun" cities on Sunday as his Republican administration prepared to intervene in urban centers

Trump condemned the Portland protests and violence in "Democratrun" cities on Sunday as his Republican administration prepared to intervene in urban centers that he said have lost control of demonstrations against racism and police brutality.

Oregon's governor and Portland's mayor, both Democrats, called the move an abuse of power by the federal government, and the western state filed a lawsuit against the US agencies involved. Portland Mayor Ted Wheeler on Sunday renewed his call for the federal troops to leave the restive city, accusing the troops of escalating the situation.

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"Their presence here is actually leading to more violence and more vandalism," Wheeler said on CNN's State of the Union program. "And it's not helping the situation at all. They're not wanted here. We haven't asked them here. In fact, we want them to leave."

The mayor added: "What I want to do is raise awareness nationally. This could happen in your city. And what we're seeing is a blatant abuse of police tactics by the federal government, by a Trump administration that's falling in the polls. This is a direct threat to our democracy."

Following the May 25 killing of George Floyd, protests have swept the United States, and Portland has witnessed nightly demonstrations against police brutality and systemic racism in the city.

Executive order

Federal law enforcement officers, using an executive order by Trump aimed at protecting US monuments, last week started cracking down on crowds gathering in Portland.

The federal offensive in the liberal city in the Pacific Northwest sparked criticism and legal challenges as videos surfaced of officers in camouflage without clear identification arresting protesters.

"We are trying to help Portland, not hurt it. Their leadership has, for months, lost control of the anarchists and agitators. They are missing in action. We must protect Federal property, AND OUR PEOPLE. These were not merely protesters, these are the real deal," Trump tweeted on Sunday.

In a letter on Sunday, the Democratic chairs of three House of Representatives committees called on the inspectors general for the Justice Department and the Department of Homeland Security to investigate the use of force by federal officers against protesters.

"The Attorney General of the United States does not have unfettered authority to direct thousands of federal law enforcement personnel to arrest and detain American citizens exercising their First Amendment rights," said the letter signed by Bennie Thompson of Mississippi, chairman of the House Committee on Homeland Security, and representatives Jerrold Nadler and Carolyn Maloney of New York, chairs of the House Judiciary, and Oversight and Reform committees, respectively.

In Denver, many gathered on Sunday at the Greek Amphitheater in Civic Center Park to show support for law enforcement, while a few hundred people in another group gathered at the State Capitol steps to protest police brutality.

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Moreover, tens of thousands workers were set to take to the streets in more than two dozen cities on Monday to protest against systemic racism and economic inequality during the pandemic. Dubbed the "Strike for Black Lives", labor unions, social and racial justice organizations from New York City to Los Angeles will participate in a range of planned actions, organizers said.

Chen Yingqun in Beijing and agencies contributed to this story.