After violence Saturday night in Portland, Ore., left a man dead, President Trump responding by threatening to take unspecified action in the city.

In one of several tweets Monday morning, Trump said, "Portland is a mess, and it has been for many years. If this joke of a mayor doesn't clean it up, we will go in and do it for them!"

The tweet came after clashes between Trump supporters, who entered the city in a caravan of hundreds of trucks, and Black Lives Matter demonstrators. Police have not released information about the victim or any suspects as of Monday morning.

Trump on Sunday tweeted his support for the pro-Trump activists, calling them "GREAT PATRIOTS."

Portland Mayor Ted Wheeler, a Democrat, on Sunday blamed Trump for the violence. "Do you seriously wonder, Mr. President," he asked, "why this is the first time in decades that America has seen this level of violence? It's you who have created the hate and the division."

Trump has been using violence in Portland; Kenosha, Wis.; and elsewhere as a campaign issue, calling for law and order, and falsely accusing Democratic opponent Joe Biden of failing to condemn the actions.

In a statement Sunday, Biden said that "Donald Trump has been president for almost four years. The temperature in the country is higher, tensions run stronger, divisions run deeper."

Biden said he condemned the violence "unequivocally."

"I condemn violence of every kind by anyone, whether on the left or the right," he said, and called on Trump to do the same.

Biden is scheduled to speak more about violence and safety from Pittsburgh on Monday afternoon.

In an excerpt from his speech released to reporters, he will say that Trump "may believe mouthing the words 'law and order' makes him strong, but his failure to call on his own supporters to stop acting as an armed militia in this country shows you how weak he is."

On Tuesday, Trump plans to visit Kenosha, where a Jacob Blake, a Black man, was seriously wounded by police last week. In a subsequent protest, two demonstrators were shot and killed and a third wounded; a 17-year-old has been charged with homicide.

Wisconsin Gov. Tony Evers has urged Trump not to come to Kenosha, saying, "I am concerned your presence will only hinder our healing."

Copyright 2020 NPR. To see more, visit https://www.npr.org.