The outcome of the US presidential election is on a knife edge, with Donald Trump and his rival Joe Biden neck and neck in key swing states.

Mr Trump, a Republican, claimed to have won and vowed to launch a Supreme Court challenge, baselessly alleging fraud. Earlier Mr Biden, a Democrat, said he was “on track” to victory.

Millions of votes remain uncounted and no candidate can credibly claim victory as yet. There is no evidence of fraud. With the nation on edge, the final result may not be known for days.

More than 100 million people cast their ballots in early voting before election day, setting the US on course for the highest turnout in a century.