BEIRUT — Russia’s Defense Ministry says its airstrike killed the Islamic State group’s spokesman and chief strategist.

The Defense Ministry says in a statement on Wednesday that its intelligence has confirmed that a Russian airstrike on Aleppo province killed 40 IS militants, including spokesman Abu Mohammed al-Adnani.

His death is a major blow to the extremist group, which has been on the retreat in Syria and Iraq.

The United States said it launched an airstrike targeting al-Adnani in the Syrian city of al-Bab, which is northeast of Aleppo. Pentagon Press Secretary Peter Cook said on Tuesday the U.S. was “still assessing the results of the strike.”

Al-Adnani persistently called for attacks against the West.