Washington DC - A Virginia man pleaded not guilty on Friday to planting pipe bombs near the Democratic and Republican Party headquarters on the eve of the January 6, 2021 US Capitol riots.

Brian Cole Jr, of Woodbridge, Virginia, was arrested in early December after a nearly five-year manhunt.

Cole (30) entered a plea of not guilty in a federal district court in Washington to charges of interstate transportation of explosives and malicious attempt to use explosives, CNN and other media outlets said.

His arrest was the first breakthrough in a case that spawned numerous conspiracy theories among the far right.

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Prosecutors, in a filing with the court, said Cole had confessed in interviews with the FBI to planting the bombs and believed the 2020 presidential election was stolen from President Donald Trump.

Democrat Joe Biden won the 2020 vote but Trump continues to falsely claim that he was the rightful winner.

The pipe bombs – placed outside the Democratic National Committee and Republican National Committee offices in Washington on the evening of January 5 – failed to detonate.

The devices were discovered by authorities the next day as Trump supporters stormed the Capitol in a bid to prevent congressional certification of Biden's election victory.

The FBI released numerous photos and video clips of a masked and hooded suspect over the years and eventually increased the reward for information leading to an arrest to half a million dollars.

The failure of law enforcement to swiftly solve the case birthed a number of conspiracy theories, including baseless accusations that the bomber may have been a US Capitol Police officer.

After taking office for a second time last January, Trump pardoned more than 1,500 people charged or convicted of taking part in the assault on the Capitol.