Russia on Thursday said its air strikes in Syria had destroyed a huge underground arms depot belonging to Hayat Tahrir Al Sham, the extremist alliance led by Al Qaeda's former Syria affiliate. "Russian aviation destroyed the largest buried arsenal of Hayat Tahrir Al Sham near Abu Duhur," defence ministry spokesman Igor Konashenkov said, referring to a town in the northwestern province of Idlib. The munitions depot was hidden underground and contained "more than a thousand tonnes of weaponry", he added. Russia said its aviation destroyed the depot using high power artillery, specially designed to destroy underground targets. The strikes also killed "49 fighters, including seven leaders of the Al Nusra Front's eastern sector", Mr Konashenkov said. Jabhat Al Nusra, or Al Nusra Front, was Al Qaeda's affiliate in Syria until mid-2016 when it broke off ties, renaming itself Jabhat Fatah Al Sham. The group then went on to found Hayat Tahrir Al Sham, which now controls large swathes of Idlib province. <strong>________________</strong> <strong>Read more:</strong> <strong>Opinion: <a href="https://www.thenational.ae/opinion/what-isil-s-rise-in-2014-tells-us-about-al-qaeda-s-potential-in-syria-today-1.622316">What ISIL's rise in 2014 tells us about Al Qaeda's potential in Syria today</a></strong> <strong>________________</strong> Mr Konashenkov's comments repeated Russia's claim on Wednesday to have <a href="https://www.thenational.ae/world/mena/head-of-syria-s-ex-qaeda-affiliate-critical-after-russia-strike-moscow-says-1.664020">seriously injured Hayat Tahrir Al Sham's leader, Abu Mohamed Al Jolani</a>, saying he was "in a coma" and that this had "thrown the terrorists of the whole Idlib province into disarray". The alliance on Wednesday denied Russia's claim, saying Jolani was in "good health". Russia, which has intervened in the Syrian war on the side of president Bashar Al Assad's regime, said on Wednesday <a href="https://www.thenational.ae/world/mena/russia-says-killed-commanders-of-ex-qaeda-affiliate-in-syria-1.662020">it had killed 12 leaders of the extremist coalition</a>, including Jolani's security chief. The Syrian regime and Russia have carried out heavy air strikes on Idlib province after a September 18 extremist attack on its military police deployed in the neighbouring province of Hama. Also on Wednesday, a video surfaced in which Al Qaeda leader Ayman Al Zawahiri called for extremists across the world to stage attacks against the United States. The Egyptian head of the terror organisation, who took over from Osama bin Laden after he was killed in 2011, is believed to be hiding out in Pakistan as his predecessor did before his death. In the 30-minute video, Al Zawahiri said the wave of so-called jihad was “expanding” and stressed the internationalism of the movement. He also called for unity among Islamic extremists, praising bin Laden for bringing together Muslims around critical issues.