"If the Russian army kills the people of Syria, then kill their people. And if they kill our soldiers, then kill their soldiers. An eye for an eye," Abu Mohamed al-Jolani, the head of Al-Nusra Front, said in an audio recording released late Monday.
He pledged that Moscow's air war in Syria, which began on September 30, would have dire consequences for Russia.
"The war in Syria will make the Russians forget the horrors that they found in Afghanistan," Jolani said, adding: "They will be shattered, with God's permission, on Syria's doorstep."
Russia has said its aerial raids are targeting the Islamic State group, a jihadist rival of Al-Nusra, as well as other extremist groups.
Moscow's strikes have concentrated on areas in northwestern Syria where Al-Nusra has a powerful presence, mostly in the province of Idlib.
A US-led air coalition fighting IS in Syria has also targeted Al-Nusra on several occasions.
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Jolani called on armed opposition groups to set aside their differences until both air wars had been defeated.
"Delay the disputes until the demise and smashing of the Western Crusader and Russian campaign on Syrian land," he said.
The jihadist chief also called for attacks on Syria's Alawite minority, the sect from which President Bashar al-Assad hails.
"I call on all armed factions to gather the highest number of shells and rockets and to hurl hundreds of rockets every day at the Nusayri villages, just like the scoundrels do to the Sunni villages and towns, to make you taste what our people are suffering," Jolani said.
Nusayri is a derogatory term for Alawites, considered by Al-Nusra's extreme interpretation of Islam to be apostates.
"When they will stop attacking our village and cities, we will stop attacking theirs," he added.