The concussive crack of stun grenades echoed through the streets of downtown Portland Saturday as groups on opposing sides of the political spectrum took to the streets.

But despite weeks of heated rhetoric, the protest — which was organized by right-wing Patriot Prayer and countered by groups on the left — resulted in little violence between the two groups. Past clashes have quickly devolved to open fistfights and mayhem.

The protest, billed ostensibly as a rally for free speech and campaign event for Joey Gibson, the leader of Patriot Prayer and Republican U.S. Senatorial candidate from Vancouver, saw hundreds of his supporters, many of whom came from out of state, bussed in from across the border decked out in helmets, crash pads and shields festooned with the Confederate battle flag.

They were met by counter-protesters from a coalition of organizations on the left including a group called Popular Mobilization, which formed recently specifically to counter Gibson's protest, another group dressed up as clowns and a cadre of antifascist activists commonly known as antifa.

Police formed barriers along Southwest Naito Parkway early in the day and effectively kept the groups separated, close enough to hurl insults, but too far to throw punches.

The biggest dust-up came when police in riot gear ordered a group of counter-protesters to disperse around 2 p.m. The group, which was tightly clustered near the intersection of Southwest Naito Parkway and Southwest Columbia Street, did not immediately leave and officers quickly began firing dozens of flash-bang grenades and rushing toward the crowd, shoving some protesters out of the street.

In a statement released Saturday night, officials said police vehicles were surrounded by the group and protesters were "throwing an unknown chemical agent as well as other projectiles at officers" prior to the use of flash-bang grenades. Police also fired pepper balls and so-called "less lethal" rounds at protesters.

The move elicited loud cheers of "USA! USA!" from the right-leaning group cordoned across the street.

After the dispersal order was given, some projectiles were thrown at police, one of which hit Eder Campuzano, a reporter from The Oregonian/OregonLive, in the head. He was bloodied, but is doing fine.

"Unfortunately, today, some people chose to commit illegal acts of violence, which required members of the Police Bureau to take action in order to keep all participants and non-participants safe," Police Chief Danielle Outlaw said in a statement. "This was a dangerous situation for all those involved, including officers, and I am disheartened that this kind of illegal behavior occurred in our beautiful city."

The protest shut down Naito Parkway, a major thoroughfare through downtown, for much of the day Saturday.

The runup to the demonstration took on an ominous tone after Gibson moved it to Tom McCall Waterfront Park, where those with permits to carry concealed weapons could legally arm themselves. Gibson also encouraged his supporters, who were legally able, to bring guns to the protest.

Throughout the day, Portland police released images of weapons collected from both sides, including knives, sticks, shields and fireworks. Unlike past demonstrations, however, Saturday's dueling events never turned into the melee that many had predicted.

At least four people were arrested during the protest, most for disorderly conduct.

Oregonian reporters Eder Campuzano, Shane Dixon Kavanaugh, Anna Spoerre, Hannah Boufford and Jim Ryan contributed to this post.

-- Kale Williams

kwilliams@oregonian.com

503-294-4048