The Syrian Observatory for Human Rights (SOHR) said air strikes were carried out by the Russian air force have killed at least 57 people in the rebel-controlled area of Maaret al-Numan town in Idlib province on Saturday.
Activists said four vacuum bombs were dropped by the Russian air force in the town of Maaret al-Numan; other air strikes were also carried out in the towns of Saraqib, Khan Sheikhoun and Maar Dabseh, in Idlib.
According to civil defense sources said the air strikes hit a court house and adjoining prison in the town of Maarat al-Numan.
The sources from Maarat al-Numan announced the victims who were mostly civilians were killed in the strikes when Russian warplanes targeted a market and residential areas.
Russia has been carrying out air strikes in Syria in support of Bashar al-Assad since September.
The building was struck with four missiles and the number of dead could increase due to the large number of wounded, the Syrian Observatory for Human Rights said.
A large number of people were also wounded in the strike, many of whom remain in critical condition, the observatory group said.