At least 39 people were killed on Saturday when an airstrike targeted a prison in a rebel-held area in Syria's northwestern province of Idlib, a monitor group reported.
The warplane targeted the prison compound and the courthouse of the town of Maret al-Numan with four rockets, said the Syrian Observatory for Human Rights.
The Britain-based watchdog said that civilians and inmates as well as rebels were among those killed in the air strike, adding that some of the wounded are in critical condition.
Other activists said the warplane that struck the prison of Maret al-Numan and the courthouse there was Russian, adding that the city is under the control of the Al Qaeda-linked Nusra Front.
The local coordination committees said the four Russian airstrikes targeted a popular marketplace and the vicinity of the courthouse in Maret al-Numan, killing 51 people. The opposition report cannot be independently verified.
Much of Idlib fell to the Jaish al-Fateh rebel group, which consists of several rebel factions, mainly the Nusra Front.
Russian warplanes have been pounding rebel positions in Syria since last September, which is by Syrian officials as effective.
