Donald Trump tasked vice-president-elect Mike Pence to head his presidential transition team yesterday, in a shake-up that also included the appointment of three of his children to the group that will shape his administration.

Pence replaces New Jersey governor Chris Christie, who had been leading the team tasked with setting up the new government.

Trump asked the team to assemble "the most highly qualified group of successful leaders who will be able to implement our change agenda in Washington," said a statement, without elaborating on the reshuffle.

Christie's reputation has been bruised by a long-running New Jersey political-revenge scandal commonly known as 'Bridgegate', although he has never been charged with any wrongdoing.

He will remain on the team as a vice-chairperson along with other top Trump advisers, including Ben Carson, former speaker of the House Newt Gingrich, and former New York mayor Rudy Giuliani - all whom have been floated in the media as potentially holding cabinet positions.

Trump's children Ivanka, Donald Jr and Eric, son-in-law Jared Kushner, PayPal founder Peter Thiel and Republican National Committee chairperson Reince Priebus will also advise Trump.

Trump will be sworn into office on Jan 20, when President Barack Obama completes his constitutionally limited second four-year term.

After three nights of mostly peaceful anti-Trump protests in cities across the country, Obama urged post-election unity yesterday.

In his Veterans Day address at Arlington National Cemetery outside Washington, he cited the US military as an example of cooperation and selflessness, calling it the "the single most diverse institution in our country."

This year, the solemn holiday followed Tuesday's stunning victory by Trump, whose populist, inflammatory rhetoric against immigrants, Muslims and other minorities stoked an especially divisive and emotional presidential race.

"When the election is over, as we search for ways to come together, to reconnect with one another and with the principles that are more enduring than transitory politics, some of our best examples are the men and women we salute on Veterans Day," Obama said.

A third night of demonstrations in Portland, Oregon, devolved into what police called a riot as demonstrators torched cars and smashed windows. Twenty-five people were arrested by authorities, who blamed the violence on a small group of anarchists, The Oregonian newspaper reported.

There also reports of arrests in Los Angeles and Baltimore, Maryland. Other demonstrations occurred in Denver, Colorado, and Minneapolis, Minnesota.

Trump at first responded to the protests with disdain, writing on Twitter on Thursday that they were "incited by the media".

Hours later had changed his tone, writing: "Love the fact that the small groups of protesters last night have passion for our great country. We will all come together and be proud!"

Since heavily favoured Democratic presidential nominee Hillary Clinton conceded defeat to Trump early Wednesday, social media has been filled with accusations of post-election violence and intimidation on both sides.

One video online appears to show a group of people in Chicago beating a man while yelling "You voted Trump!"

The morning after the election, the New York University Muslim Students Association wrote on Facebook that 'Trump' had been scrawled on the door of a prayer room.

In a separate incident that day, students at a middle school in Michigan began chanting "build a wall" in the school cafeteria, in reference to Trump's pledge to build a wall to stop illegal crossings at the Mexican border.

Harry Reid, the top Senate Democrat, ripped into the president-elect yesterday, saying "the forces of hate and bigotry" have been emboldened by his election.

At the military cemetery, Obama urged Americans to "practice kindness" and consider that even people not now in uniform could be veterans who served "a year or a decade or a generation ago."

"We can show how much we love our country," he said, "by loving our neighbours as ourselves."

"I want a country that loves each other," Trump told the Wall Street Journal yesterday. "I want to stress that."

Trump and his family will appear tomorrow on the news magazine show '60 Minutes'.

- dpa