The Enhanced Paveway III (EPW III) with a 2,000lb deep penetration warhead was deployed to attack a large complex of tunnels and bunkers dug into a terraced hillside above the Euphrates River in western Iraq.
The MoD said RAF Tornado GR4 fighter bombers based at RAF Akrotiri in Cyprus had scored hits with a pair of EPW IIIs on two entrances to the bunker networks.
RAF aircraft involved in the campaign normally carry the smaller Paveway IV guided bombs and Brimstone missiles which can be carried in greater numbers and are considered more useful for close air support missions.
"The EPW III has been held in reserve for use if needed against particularly challenging underground or hardened targets," the MoD said in a statement posted on its website.
The EPW III was designed for use against aircraft shelters, bridges and military command centres in all weather conditions, according to HIS Jane's information group.
It was developed in response to the experience of the 1999 Kosovo campaign when the guided bombs in use at the time were severely hampered by bad weather and by smoke around targets.
