Scattered protests took place from Washington DC to Washington state in the hours after polls closed in the US elections, but there were no signs of widespread unrest or violence.

The outcome of the hard-fought contest for the presidency remained undecided on Wednesday, stirring worries that prolonged uncertainty could spark conflict.

But overnight demonstrations in cities including Seattle, Washington and New York remained largely peaceful.

In Washington, more than 1,000 people protesting against Donald Trump converged on Black Lives Matter Plaza on Tuesday night, a block from the White House, while hundreds more marched through the city centre, blocking traffic and setting off fireworks.

Protesters shouted “Whose streets? Our streets!” and “If we don’t get no justice, they don’t get no peace!”

Groups of teenagers danced in the street as onlookers cheered. Large banners, including one reading “Trump lies all the time”, were unfurled.

At one point, the marchers stabbed the tyres of a parked police van to flatten them.

Hundreds of people marched in anti-Trump demonstrations in Portland, Oregon, and Seattle, with several arrested.

“This is what democracy looks like,” protesters chanted in Portland, where organisers said the demonstration would be peaceful and that regardless of the presidential election result, they would continue protesting in support of racial justice.

The sheriff’s office said some protesters were openly carrying guns.

Oregon governor Kate Brown had put the National Guard on standby since Portland has seen almost nightly protests since the death of George Floyd under a Minneapolis police officer’s knee in May.

Portland mayor Ted Wheeler said on Twitter that there would be “no tolerance for any violence, intimidation or criminal destruction”, and that people should be “safe while using their voice to advocate for their perspective”.

In Seattle, police said they had arrested several people, including someone who put nails in a road and another who drove over a barricade and into a police bike lane. No one was injured.

Hundreds of businesses in cities across the US boarded up their doors and windows ahead of the election, fearing the vote could lead to the sort of violence that broke out after Mr Floyd’s death.

“Some people would like to cause mayhem and trouble,” Washington mayor Muriel Bowser said earlier in the day. She said she had never seen so many businesses being boarded up: “That all saddens me.”