As many as 1,000 police officers were called in to provide security in downtown Portland, on Saturday, Aug. 17, as two competing political groups confronted one another with rallies.

Antifa, an anti-government protest group with a following in the Portland area, gathered to march and confront a political right-wing rally, led by another group called “Proud Boys,” near the SW Park area of the city.

Both groups beat drums and called out their slogans, as police tried to keep the two groups separated by declaring the streets and sidewalks off limits. The demonstrations, while noisy, were uneventful, through the early afternoon.

Police had proactively confiscated weapons from rally goers, which reportedly included cans of bear spray, sticks, and even small flagpoles that police construed to potentially be used as weapons.

Some minor clashes did take place later, however, resulting in at least 13 arrests. Further details have not yet been made available by Portland authorities. Police reported that one person was injured and taken to a nearby hospital.

In one incident, a group of antifa activists were filmed using rocks to smash the windows on a bus that had carried Proud Boys demonstrators into the city center.

Around 4 p.m. in the afternoon, police declared a “civil disturbance,” due in part to interference with local traffic. Both groups were then ordered to disperse.

President Trump has been an outspoken critic of antifa in recent weeks and has even threatened to categorize the group as a terrorist organization.

On Saturday morning, he posted on Twitter, “Major consideration is being given to naming ANTIFA an ‘ORGANIZATION OF TERROR.’ Portland is being watched very closely. Hopefully the Mayor will be able to properly do his job!”