BAKU, Azerbaijan — The U.S. and British embassies suspended operations Monday in Baku, where the government said it thwarted a radical Islamic group's plot to conduct a "large-scale horrifying terror attack" against diplomatic missions and government buildings.

The Azerbaijani National Security Ministry said one suspect was killed and several others were detained in a weekend sweep outside the capital. The ministry said the Islamic group included an army lieutenant who stole 20 hand grenades, a machine gun, four assault rifles and ammunition from his military unit and made them available for the planned attack.

The British Embassy in Baku temporarily closed Monday, and the U.S. Embassy sent out an announcement to American citizens saying it had closed its consular office for an indefinite period because of a security threat. No specifics were given.