2020 election may be held under 'martial law', warns Oregon senator

43 arrests have been made by federal agents in Portland since 4 July

Oregon senator Ron Wyden has warned the US presidential election could be held under martial law after federal police officers clashed with rioters during the 54th night of protests in his state's largest city.

Speaking at Senate intelligence committee hearing on Wednesday, Mr Wyden said Portland had been "invaded by militarized law enforcement".

"If the line is not drawn in the sand right now, America may be staring down the barrel of martial law in the middle of a presidential election," Mr Wyden said.

Donald Trump said on Monday that he was looking at deploying federal agents to Chicago, New York Philadelphia and other US cities run by the "radical left" experiencing a rise in violent crime.

"Portland was totally out of control. The Democrats the liberal Democrats running the place had no idea what they were doing. They were ripping down, for 51 days, ripping down that city. Destroying the city. Looting it," Mr Trump said.

Officers from the US Customs and Border Protection's Border Patrol Tactical Unit (BORTAC) were deployed to Portland ostensibly to defend federal buildings. The agency claims protesters are armed with slingshots, fireworks, lasers, baseball bats, metal pipes, glass bottles and other improvised weapons.

Since 4 July, there have been 43 federal arrests in Portland by Department of Homeland Security (DHS), US Marshals and other federal law enforcement agencies, DHS acting secretary Chad Wolf said.

When asked if more agents would be sent around the country as the president indicated, Mr Wolf said on Tuesday that his department would maintain its existing presence in major cities across the country and surge if needed, but that was a different mission than what was happening in Portland.

"Portland, which is unique. Violent anarchists in Portland vs normal city criminal activity, behaviour by gangs, by criminal elements throughout the country. Those are two different things. The president, you can certainly ask the White House and others, that's what he was referring to," Mr Wolf said.

At a Senate select committee on intelligence open hearing on Wednesday, Mr Wyden asked the Department of Justice's nomination Patrick Hovakimian if the federal government's actions in Portland were legal.

Mr Hovakimian said free speech and free assembly were sacrosanct, and that it was a bedrock principle that neither law enforcement nor the intelligence community should target or surveil Americans protected under the first amendment.

"Peaceful protest is one thing and violence is another," Mr Hovakimian said.

Mr Wyden said the federal government's presence in Portland was unconstitutional and that the law shouldn't be used as a smokescreen to justify an invasion over the objections of local officials.

Federal Protective Service deputy director of operations, Richard Cline, said they have legal authority under title 40 section 1315 of the US Code to do investigations both on and off federal property based on alleged crimes that occur on federal property.

"Since May 28th... we've observed over 425 demonstrations and 260 attacks at federal facilities across the country. These attacks include bullets fired at federal facilities, arson, and objects thrown through windows," Mr Cline said.