A MAN HAS been arrested near Washington DC’s iconic Capitol building today, as police foiled an alleged plot to mount a suicide attack on the home of the US Congress.

US Capitol Police say their officers and FBI officials arrested the man in a sting operation.

The man of Moroccan descent and in his 30s was taken into custody on his way to mount what he believed would be a suicide attack, the Washington Post reports. He had an explosive vest with him.

However, Justice Department spokesman Dean Boyd said the suspect was closely monitored by law enforcement, and the purported explosives were deactivated, so the public was not in danger.

Fox News reports that the man believed he was being assisted by members of al-Qaeda who were in fact undercover FBI operatives.

Two people briefed on the matter told The Associated Press he was not arrested on the Capitol grounds, and the FBI has had him under surveillance around the clock for several weeks. They spoke on a condition of anonymity because they were not authorized to speak on the record.

A US law enforcement official said the person arrested was canvassing the US Capitol with violent intentions. He was not believed to have any known connections to al-Qaeda. It was not immediately clear whether he was a US citizen.

- Additional reporting from AP