Authorities in the former Soviet republic of Azerbaijan claimed today to have thwarted a "large-scale horrifying terror attack" planned against government targets and Western diplomatic missions in the capital.

Both the British and American embassies were closed today and the Foreign Office said that it was reviewing its travel advice - although officials refused to give any details of the threat.

The Azeri National Security Ministry said that the alleged plot had been formulated by a radical Islamic group. It said that one suspect was killed and several others were detained in a weekend sweep outside the capital.

The ministry said in a statement that the radical Islamic group included an army lieutenant who had stolen 20 hand grenades, a machine gun, four assault rifles and ammunition from his military unit and made them available for the planned attack.

Security forces tracked down the group and arrested several of its members during a sweep on Saturday in the village of Mastaga about 20 miles northeast of Baku. One member of the group offered resistance to the arrest and was killed, the statement said. The ministry said that a hunt for other members of the group was still under way.

Arif Babayev, a spokesman for the security ministry, told the Associated Press that a group of radical Wahhabi Muslims had planned to launch a “terror attack against several government structures in Baku and the US Embassy”.

The US Embassy sent out an announcement to American citizens saying that it had closed its consular office for an indefinite period because of a security threat and encouraging them to “maintain a high level of vigilance”.

The British Embassy was also closed today, along with other offices in the same Landmark building, including those of Norway’s StatoilHydro ASA and BP Azerbaijan.

Azerbaijan is an oil-producing, mainly Muslim republic of eight million people on the western shore of the Caspian Sea, wedged between Iran, Turkey and Russia. Authorities there have in the past years arrested dozens of people suspected of links to Islamist militants, but the country has no history of militant violence against Western targets.

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