A man who appeared drunk was arrested after threatening to set off what turned out to be a fake explosive belt in the headquarters of Jordan's largest opposition group on Monday, officials said.
The Islamic Action Front, the political arm of the powerful Muslim Brotherhood, has been organizing protests demanding reform in Jordan.
Islamic Action Front leader Jaafar Sabti said the man smelled of alcohol and displayed what he said was an explosives belt.
Bomb experts found the belt was fake, police said. They said the man was being questioned for "inciting fear of an attempted attack."
The IAF and the Muslim Brotherhood have been taking to the streets across Jordan, pressing demands for change.
Suicide bombings are rare in Jordan but in November 2005 a triple hotel suicide bombing later claimed by al-Qaida in Iraq killed 60 people.
Sameer N. Yacoub contributed to this report.