A 29-year-old Moroccan man was arrested in Washington D.C. on Friday for trying to execute a suicide attack against the US Capitol building, which houses both chambers of Congress.

The suspect, identified as Amine El Khalifi, had been under surveillance by the Federal Bureau of Investigation (FBI) for a year. El Khalifi had purchased a fake suicide vest from undercover FBI agents posing as members of al-Qaeda.

"Explosives the suspect allegedly sought to use in connection with the plot had been rendered inoperable by law enforcement and posed no threat to the public," Justice Department spokesman Dean Boyd said.

El Khalifi was wearing the fake suicide vest and carrying an inoperable firearm when he was arrested near the US Capitol.

"Amine El Khalifi sought to blow himself up in the US Capitol Building," US Attorney Neil MacBride said in an official release. "El Khalifi allegedly believed he was working with al-Qaeda and devised the plot, the targets and the methods on his own."

'Brazen' plot

The Moroccan national came to the US when he was 16 years old and had overstayed his visitor visa by years, according to anonymous officials cited by the news agency Reuters. He was a resident of Alexandria, Virginia, bordering Washington D.C.

Authorities briefed US lawmakers, who were gathered in the Capitol building to debate and vote on legislation.

"The brazen nature of this plot - targeting the US Capitol building with the aim of killing innocent people and desecrating a symbol of our democracy - is disturbing," Republican Senator Susan Collins said in a statement.

"While we are still learning details, this plot appears to be yet another example of radicalized extremists attempting to attack Americans from within our borders," she added.

slk/srs (AP, AFP, Reuters)