Pro-Trump and BLM protesters clash in violent scenes as experts warn election will bring social unrest

Violent clashes between right- and left-wing groups broke out following the 102nd day of unrest in Oregon and just over a week after the conflict escalated with the Antifa killing of a Patriot Prayer member.

State police arrested two men from pro-Trump groups that charged at BLM activists counter-protesting an "American Lives Matter" rally in the Oregon Capitol of Salem.

It came following the 45-mile Oregon For Trump 2020 Labor Day Cruise Rally from Portland as a smaller group of about 100 supporters, including members of the Proud Boys, faced off against about 20 counter-protesters waving flags supporting Black Lives Matter and Antifa, according to video posted to social media.

A section of the Trump-supporting group broke away to chase down at least two counter-demonstrators after two groups exchanged pepper spray between each other, according to the Associated Press.

In one clash captured on video, a BLM supporter can be seen being pushed to the ground and punched by one man as he's soon pulled off by others. A woman then sprays him in the eyes while on the ground.

"That's for everything you f***ing did to me b*itch, I told you I'd get you," she says as the man appears to say "I'm sorry" while protecting his head in the foetal position.

Soon after another BLM supporter, Eddie Coleman, is chased down and pushed over before Oregon State Police and Salem Police rush in and make the two arrests.

"I came out because one of my friends on Twitter requested back-up," Mr Coleman said in an interview with journalist Mike Baker posted to Twitter following the clash.

"I was walking across like the main area and a bunch of people rushed at me yelling slurs and, um, firing paintball guns at me and like empty rounds of something, I don't know. And when I stood my ground finally one of them pushed me to the ground and hit my face repeatedly and kneeled on my chest with his full weight."

Two men were charged with misdemeanour assault and later released.

Last week, Michael Forest Reinoehl, the self-proclaimed "100% Antifa" suspect in the killing of Patriot Prayer member Aaron "Jay" Danielson was killed in a shoot-out with police as they attempted to arrest him.

The escalation of violence comes as experts warn uncertainty over mail-in votes could spark social unrest as more than a half of Democrats, compared to one-quarter of Republicans, plan to vote by mail-in ballot.

Battleground states like Arizona, Florida and North Carolina will begin processing mail-in ballots before election day but key swing states like Michigan, Pennsylvania and Wisconsin prohibit counting ballots until after election Day.

“If the election comes down to these states, and everyone is waiting on results, I'm concerned about social unrest. This is especially true if Trump is ahead on election day,” Rick Hasen, an elections expert and law professor at the University of California at Irvine, told Reuters.