“Saboteurs exploded a bomb, setting oil well number 20 on fire," Lieutenant Colonel Hammudi Ali of the state-owned North Oil Company’s security force was reported as saying in an AFP report.

"The firefighters are still trying to put out the fires, but so far they haven’t managed to extinguish a single one.”

Guards prevented a second sabotage attempt overnight, killing one assailant and wounding another, at a well further west, according another oilfield security force officer, Colonel Nawzad Ahmed.

In an audio message posted on the Internet a week ago, a man claiming to be insurgent leader Abu Mussab al-Zarqawi urged attacks on oil facilities around Iraq.