Washington: Riot police were out in force in Portland, Oregon, on Sunday, as pro and anti-Trump supporters faced off in the wake of two murders that are the latest manifestation of a disturbing wave of real and threatened political violence in the United States.

When the pushing, shoving and name-calling was over, there were a reported 14 arrests after helmeted police resorted to noise grenades and tear gas to keep the protests apart. But the police said they were reacting to sentiments expressed on the weapon-of-choice championed by Donald Trump and a good many others grappling with, or defending, his elevation to the presidency: social media.

Portland has been a tinderbox since May 26, when three commuters went to the assistance of two girls – one black, the other wearing a Muslim headdress – who were being taunted verbally as they travelled on a city train.

Their tormentor produced a knife, killing two of the men. The 35-year-old alleged assailant, Jeremy Christian, was charged with double murder in what the FBI is treating as a hate crime.