"Baghdadi's death is not the end of fighting Deash (Arabic acronym for IS) terrorism but just the end of a chapter," government spokesman Ali Rabiei said in a tweet.

"(IS terrorism) is still growing and evident. Growing via American policies and regional petrodollars, and evident in takfiri (Sunni Muslim extremist) ideology. These three sources must be extinguished," he added.

US President Donald Trump announced Baghdadi's death on Sunday during a nighttime raid by US special forces deep outside the village of Barisha in Idlib province, northwestern Syria.

He said that US forces killed a "large number" of IS militants during the raid which culminated in cornerning Baghdadi in a tunnel, where he set off a suicide vest.

The raid -- which required flying more than an hour by helicopter in both directions from an undisclosed base -- had been accomplished by help from Russia, Syria, Turkey and Iraq, according to Trump.

In 2014, Iran sent the commander of the elite Quds Force of its Islamic Revolutionary Guard Corps, Major General Qasem Soleimani and "military advisers" to Iraq to help it in the fight against IS.