Law enforcement officers far outnumbered protesters at state capitol grounds on Sunday, as few Trump supporters who believe the president's false claim that he won the 2020 election turned out for what authorities feared could be violent demonstrations.

More than a dozen states activated National Guard troops to help secure their capitol buildings following an FBI warning of armed demonstrations, with right-wing extremists emboldened by the deadly attack on the US Capitol in Washington on January 6.

Security officials had eyed Sunday as the first major flashpoint, as the anti-government "boogaloo" movement made plans weeks ago to hold rallies in all 50 states.

But by Sunday evening, only small gatherings of demonstrators had taken to the streets alongside much larger crowds of law-enforcement officers and media personnel.

"It was a non-event today and we are glad it was," said Troy Thompson, spokesman for the Department of General Services, the agency that protects the Pennsylvania Capitol in Harrisburg.

Tens of thousands of security personnel from the National Guard and law-enforcement agencies descended in recent days upon Washington, DC, to bolster security ahead of Wednesday's ceremony, when Joe Biden will relieve departing Republican President Donald Trump.

General Daniel Hokanson, who heads the National Guard Bureau, was asked by CBS News on Sunday if troops were being checked as they arrived in Washington.

"In coordination with the Secret Service and the FBI, they're screening all the personnel that are coming in," Hokanson said. The image of Washington as a fortress has unsettled US pride over the traditionally peaceful transfer of power.

It was unclear how much the FBI warning and robust security presence around the country on Sunday led protesters to cancel plans, reports AFP.