The US has laughed off claims that a Russian air strike killed the Islamic State's (Isis) chief strategist, Abu Muhammad al-Adnani. It follows claims by Moscow on Wednesday (31 August) that a Russian Su-34 bomber killed up to 40 militants, including al-Adnani, during a raid on the village of Umm Hawsh, 15 miles north of Aleppo.

"It would be laughable but for the very real humanitarian suffering Russia has inflicted," an unidentified US defence official saidon 31 August.

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"We stand by the statement we made yesterday. We conducted a strike that targeted al-Adnani. We are assessing the results of that strike." the official told CNN. Another US defence official told Reuters – on condition of anonymity – that "Russia's claim is a joke".

Pentagon spokesman Peter Cook said: "We have no information to support Russia's claim that they also carried out a strike against Adnani."

Cook added: "Al-Adnani has served as principal architect of Isis' external operations and as Isis' chief spokesman. He has coordinated the movement of Isis fighters, directly encouraged lone-wolf attacks on civilians and members of the military and actively recruited new Isis members."

The US targeted al-Adnani in a strike on Tuesday (30 August) using a Predator drone, which unleashed a Hellfire missile on a vehicle believed to be carrying the IS (Daesh) figure. While the US did not immediately confirm al-Adnani's death, such assessments can often take days and announcements are sometimes pipped by militant organisations.

Al-Adnani's death was acknowledged by the IS-linked Amaq news agency, which reported that he was killed "while surveying the operations to repel the military campaigns against Aleppo."

IS has vowed to avenge al-Adnani's death and said: "After a journey filled with sacrifice and fight against non-believers, the Syrian Gallant knight, Abu Muhammad al-Adnani, joined the convoy of martyr leaders.

"To the filthy and coward nonbelievers and to the holders of the Christ emblem, we bring the good news, which will keep them awake, that a new generation in the Islamic State ... that loves death more than life ... this generation will only grow steadfast on the path to Jihad, stay determined to seek revenge and be violent toward them."

Isis Islamic State Russia Syria