"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 Idlib province.
The munitions depot was hidden underground and contained "more than a thousand tonnes of weaponry," he said in statement.
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."
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The statement repeated Russia's claim yesterday to have seriously injured Hayat Tahrir al-Sham's leader Abu Mohamed al-Jolani, saying he was "in a coma" and that this had "thrown the terrorists of the whole Idlib province into disarray."
The jihadist-led alliance yesterday denied Russia's claim, saying that Jolani was in "good health."
Russia, which has intervened in the Syrian civil war on the side of Bashar al-Assad's regime, said yesterday it had killed 12 leaders of the jihadist coalition including Jolani's security chief.