Russia's Defense Ministry says that a Russian air strike in the province of Aleppo, Syria, killed a top Islamic State (IS) commander, Abu Muhammad al-Adnani.

The ministry said on August 31 that at least 40 IS militants were killed a series of air strikes, including the deadly attack against Adnani.

On August 30, the Pentagon confirmed that it carried out an air strike targeting Adnani.

But the Pentagon stopped short of confirming reports of his death, saying U.S. military officials were still assessing the results of the U.S. attack.

Quoting a "military source," the IS-affiliated Amaq news agency reported on August 30 that Adnani was killed "while surveying operations to repel the military campaigns against Aleppo," without elaborating.

Pentagon spokesman Peter Cook described Adnani as the "principal architect" of the IS group's external operations and its main spokesman.

Cook said Adnani "coordinated the movement” of IS fighters, “directly encouraged lone-wolf attacks on civilians and members of the military,” and actively recruited militant fighters.

Syrian-born Adnani is reportedly one of the IS group's longest-serving officials and most senior officials.

American officials said he was also one of the first foreign fighters to oppose the presence of U.S.-led forces in Iraq after the 2003 invasion.

He had a U.S. bounty of $5 million on his head.

The IS has suffered a string of defeats in recent weeks, including in the province of Aleppo, where a Turkish-led military incursion launched on August 23 drove the militants out of the border town of Jarablus.

Based on reporting by Reuters, AP, and AFP