The strikes on Saturday targeted an Al-Nusra Front building near a popular market in northwestern Idlib province, according to the Syrian Observatory for Human Rights.
The complex in Maarat Al-Numan housed the group's religious court and a jail.
The dead included 23 Al-Nusra fighters and six non-jihadist rebels who were in the building.
Another 52 people -- including civilians and prisoners in the complex -- were also killed.
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Russian warplanes have been conducting air strikes against the Islamic State organisation and "other terrorist groups" in Syria since September 30.
Although Al-Nusra and IS are both jihadist organisations, they are fierce rivals and regularly clash in Syria.
Al-Nusra also has tense relationships with non-jihadist rebel groups that oppose its extreme interpretation of Islamic law.
In Idlib, it heads a coalition of Islamist and rebel groups known as the Army of Conquest which has expelled regime forces from the province.
Syria's conflict first erupted with anti-government demonstrations in March 2011 but expanded into a war that has left more than 260,000 people dead.