UK Targets ISIS Bunker With Royal Air Force’s Largest Bombs

— -- The United Kingdom's Royal Air Force (RAF) has ramped up its bombing campaign against ISIS.

Enhanced Paveway III (EPW III) bombs, the largest in RAF's arsenal, successfully hit two entrances to an underground bunker as part of the coalition's efforts to combat ISIS.

The strikes, which occurred on April 21, targeted a large complex of tunnels and bunkers in the terraced hillsides above the Euphrates in western Iraq, according to a press release from the Ministry of Defense.

There were no civilian casualties, a spokesperson for the Ministry of Defense confirmed to ABC News.

Typically these "bunker buster" bombs are used to strike underground targets that have been reinforced to protect from aerial bombardment.

"Our aircraft normally carry the smaller Paveway IV guided bombs (500 lbs) and Brimstone missiles, which can be carried in larger numbers and are more useful for close air support missions," the Ministry of Defense said in the statement. "The EPW III has been held in reserve for use if needed against particularly challenging underground or hardened targets."

The last time RAF used these bombs was in 2011 against the former Libyan dictator Muammar Gaddafi.

The British, a key member of the coalition against ISIS, recently doubled the number of aircraft at its base in Cyprus to sixteen.

ABC News' Luis Martinez and Lena Masri contributed to this report.