Left- and rightwing demonstrators marched again in Oregon, leading to blocked traffic and skirmishes with law enforcementPolice use pepper spray as multiple groups protest in downtown Portland. Photograph: Dave Killen/APPolice declared a civil disturbance in Portland, Oregon, on Saturday afternoon, after a day of duelling political protests culminated in brawls and standoffs between demonstrators and law enforcement.By 3pm more than 400 leftwing marchers had blocked traffic in parts of downtown. Demonstrators occupied streets adjacent to Pioneer Courthouse Square, where police repeatedly warned them to disperse. Some were involved in altercations with officers in riot gear who deployed pepper spray and made three arrests. Others clashed intermittently with rightwing protesters.The leftwing march evolved from an early afternoon rally in a downtown park organized as a counter-protest to two rightwing events. The rally organized by local group PopMob began as a vegan milkshake-themed rally and dance party, in response to rallies announced by the Proud Boys and by a group led by Haley Adams, a local rightwing figure. Adams’ event attracted around 25 people.Milkshakes, recently used around the world as a symbolic weapon against prominent figures on the far right, became a theme of the day. Portland police claimed without offering evidence that some milkshake cups had been filled with quick-drying cement.Actual milkshakes were used by leftwing protesters. A videographer and editor for the rightwing magazine Quillette, Andy Ngo, had one dumped on him early in the day.Another incident involving Ngo captured attention, particularly on the right. Widely shared video taken by the Oregonian journalist Jim Ryan appeared to show Ngo being hit by counter-protesters and sprayed with silly string. Ryan tweeted: “Didn’t see how this started, but Ngo got roughed up.”Ngo said he had been attacked and hospitalised, and posted to social media pictures of apparent facial abrasions. With significant backing from rightwing media and political figures, by late Saturday a crowdfunding website for Ngo had raised more than $60,000.Notable by his absence on Saturday was the local rightwing figurehead Joey Gibson, who had announced that he would be leading a second amendment rights rally in Goldendale, Washington.After a violent incident at a Portland bar, Cider Riot, after May Day celebrations, Gibson was the subject of a million dollar lawsuit brought by the bar’s owners. He has made videos asking viewers to donate to a crowdfunding campaign, to cover his legal expenses.