Weary from one of the most bruising US presidential races in modern times, Republican and Democratic voters alike were in a state of high anxiety on Wednesday with the election outcome still unsettled a day after polls closed.

President Donald Trump's false declaration of victory in the early hours of Wednesday, as ballot counting continued in several pivotal states, roiled supporters of Democratic challenger Joe Biden.

Biden supporters expressed heightened fears the Republican incumbent might not accept the election result if he were to lose. Many in Trump's voter base, meanwhile, echoed his unsubstantiated allegations of widespread electoral tampering.

"Election fraud is running rampant," said Trump voter Jimmie Boyd, 48, a North Carolina gun rights activist with ties to local militia groups. Boyd said he...