Demonstrators stand outside the Mark O. Hatfield United States Courthouse during the protest against racial injustice and police brutality on July 31, 2020 in Portland, Oregon. (PHOTO / AFP)

Portland, Oregon, again is at the center of heated political discourse in the United States after a man was shot and killed over the weekend during a clash between protesters and supporters of US President Donald Trump.

The mayor of Portland and the president exchanged a slew of insults on Sunday on the situation in the city.

The man who died was a member of Patriot Prayer, a right-wing group. The clashes ensued when a caravan of about 600 vehicles with Trump 2020 and US flags rippling descended on the Pacific Northwest city.

"GREAT PATRIOTS!" Trump wrote on Twitter as he shared video of his supporters driving into Portland to confront the protesters.

Portland has been convulsed by protests and violence since the May 25 death of George Floyd, a black man, in Minneapolis police custody.

The violence in several cities has become a central campaign issue in the Nov 3 presidential election. Trump and Vice-President Mike Pence spoke harshly of the unrest in their acceptance speeches at the Republican National Convention last week, pointing fingers at the Democratic leadership in those cities.

Portland has been convulsed by protests and violence since the May 25 death of George Floyd, a black man, in Minneapolis police custody

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Democratic presidential nominee Joe Biden on Sunday condemned the violence in Portland.

"The deadly violence we saw overnight in Portland is unacceptable. Shooting in the streets of a great American city is unacceptable. I condemn this violence unequivocally. I condemn violence of every kind by anyone, whether on the left or the right," Biden said in a statement.

"And I challenge Donald Trump to do the same."

"We must not become a country at war with ourselves," the former United States vice-president continued, while accusing his Republican rival Trump of "fanning the flames of hate and division in our society and using the politics of fear to whip up his supporters".

Fires and vandalism

The tension already was heightened nationally after Jacob Blake, another black man, was shot in the back by police in Kenosha, Wisconsin, on Aug 23. Protests erupted in the days following, with two people fatally shot and a third wounded on the streets of the small Midwestern city, whose business district was rocked by fires and vandalism. A 17-year-old from Illinois was charged in the shootings.

Trump is scheduled to visit Kenosha on Tuesday and is trying to arrange a meeting with Blake's family members, according to his daughter-in-law Lara Trump, who appeared on Fox News on Sunday.

Wisconsin Lieutenant Governor Mandela Barnes told CNN that the visit would not be helpful.

"They centered an entire convention around creating more animosity and creating more division around what's going on in Kenosha," she said.

READ MORE: Portland braces for escalation of violence after shooting

"So I don't know how, given any of the previous statements that the president made, that he intends to come here to be helpful, and we absolutely don't need that right now."

In a string of tweets on Sunday, Trump fired off at Portland's Democratic Mayor Ted Wheeler, reiterating his "law and order" message, a central theme of his reelection bid.

"The people of Portland, like all other cities & parts of our great Country, want Law & Order," the president wrote.

"Ted Wheeler, the wacky Radical Left Do Nothing Democrat Mayor of Portland, who has watched great death and destruction of his City during his tenure, thinks this lawless situation should go on forever."

Wheeler, in a news conference on Sunday afternoon, criticized Trump's stance on racial justice, saying: "It's you who has not found a way to say the names of black people killed by police officers."

Agencies contributed to this story.