Security forces have arrested 20 members of a cell affiliated to the Believing Youth rebels who had been plotting attacks, the Defense Ministry said yesterday. One of those arrested was involved in a May 7 grenade attack against a bus of the air defense academy in Sanaa that wounded five military personnel, including three Iraqi experts who teach at the academy, said the ministry's September 26 website. Various types of weapons were seized from the group, it said. The group are followers of Badruddin Al-Houthi who were involved in two weeks of fighting with government forces in the mountainous northwest last month that left some 280 people dead. A security source said yesterday that preliminary investigations with Al-Houthi supporters showed they were plotting to assassinate political and military figures as well as target vital facilities in Sanaa. Authorities said on May 5 they had arrested 11 rebels suspected of carrying out attacks in the capital. The security source said authorities had identified all insurgents from the outlawed Believing Youth movement charged with carrying out acts of sabotage but many were still at large.