A Russian military journalist published pictures of destroyed aircraft at al-Humaimim base, which was shelled by opposition gunmen.
Roman Sabunkov published photos on social media after reports of al Qaeda bombing.
The Russian Defense Ministry has acknowledged the attack on al-Qaeda on December 31, killing two military personnel but denied that it led to the destruction of aircraft.
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The Russian newspaper Kommersant said on the basis of military diplomatic sources that seven aircraft were destroyed in the strongest attack on the base near Lattakia.
They described the attackers as "Islamic militants."
The losses were six Su-24, one Su-35S, one An-72 and one An-30, as well as an Mi-8 helicopter, Sabunkov said on the Vikontakti website.
He told the BBC he had obtained the photos from a reliable source.
The Hameimim base is the main base from which Russian planes fly to launch raids on opposition sites.
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Russian air strikes reportedly killed many civilians, a charge Moscow denies.
Russian forces have long-range anti-aircraft missile batteries at the base and say they are now immune to attacks.