At least eight children and a teacher were killed after a Russian airstrike hit a school in Syria’s Aleppo province, the Syrian Observatory for Human Rights said Monday. The news comes days after Russia denied allegations that its airstrikes have killed civilians.

The U.K.-based monitoring group reportedly said that the airstrike took place in the town of Anjara, injuring at least 20 people, most of them children and some teachers. Fierce exchanges of gunfire and rocket erupted Sunday in the war-torn city in the northern Syrian province, Agence France-Presse reported.

Russia has launched about 5,200 sorties in Syria over the past three months. According to a December report by the Syrian Observatory for Human Rights, more than 2,300 people, including 792 civilians, have been killed since Russia began airstrikes in September.

Russia, a staunch ally of Syrian President Bashar Assad's regime, said that its military presence in the country is aimed at defeating the Islamic State group, also known as ISIS, and other “terrorists.” However, several countries have argued that Russia’s attack in Syria is intended at keeping its long-term ally Assad in power.

Russia intensified its airstrikes against ISIS strongholds in Syria after the Sunni militant group claimed responsibility in November for downing Russia’s Metrojet Flight 9268 over Egypt, killing all 224 people on board.

Last month, Amnesty International released a report alleging that Russian airstrikes have killed at least 200 civilians in the two months to the end of November.

Russia's Deputy Foreign Minister Mikhail Bogdanov dismissed the Amnesty report that termed Russia’s military actions in Syria “war crimes.” Bogdanov reportedly said that the report contains "fake information" and "trite clichés.”