FBI agents arrested a 29-year-old man in a sting operation Friday night who planned a suicide bombing attack on Capitol Hill in Washington DC.

Justice Department spokesman Dean Boyd told reporters the suspect had been closely monitored by law enforcement while planning to detonate what he believed were explosives. He allegedly prayed in a Washington mosque shortly before his arrest.

The suspect was allegedly of Moroccan descent and has spent 12 years in the United States, but it is not clear whether he has U.S. citizenship. He had been under surveillance for several weeks, sources said, and had considered a large number of targets, including military bases and synagogues.

According to a Fox News report, the suspect believed the undercover FBI agents with whom he was in contact were associates of the international Al Qaeda terrorist organization.

It is not clear how the FBI learned of his intentions.