RAF jets flying from a base in Qatar were called in to cover the retreat of an Iraqi government force routed by religious extremists near the Shi'ite holy city of Najaf on Sunday.

The Tornado GR4 fighter bombers flew from al Udeid airbase near Doha as Iraqi soldiers and policemen were pinned down by heavily-armed members of the "Soldiers of Heaven" cult dug in among orchards on the edge of the city.

The RAF joined US F-16s in low-level passes over the positions, dropping 500lb bombs to allow the Iraqi troops to escape and reorganise.

At least six government soldiers were killed and 30 wounded by fire as they went in to investigate reports that the messianic cult planned to assassinate leading Shi'ite clerics during the festival of Ashura.

The Iraqi battalion was ambushed by up to 800 extremists armed with heavy machine-guns, mortars and rocket-propelled grenades.

US ground troops and Apache gunships were called into action late on Sunday and throughout Monday.

The RAF keeps detachments of Tornados, Nimrod reconnaissance and strategic transport aircraft at Al Udeid airbase as a way-station for operations in Iraq and Afghanistan.

The current strike aircraft are believed to be part of 9 Squadron.