Fifteen civilians were killed and another 22 injured on Tuesday evening when Russian warplanes struck two villages in an opposition-held district of Syria's northwestern Aleppo province, local Civil Defense sources told Anadolu Agency.According to the sources, Russian warplanes targeted the villages of Kafr Kalbin and Kafr Khashir, both located in Aleppo's opposition-held Tel Rifaat district.Earlier Tuesday, Russian warplanes had also targeted residential parts of Syria's northwestern Idlib province, likewise killing some 15 civilians and injuring more than a dozen others.Abu Mahmoud, a member of a local coordination committee in Tel Rifaat, said Russia had carried out more than 20 airstrikes in the district and in neighboring villages on Tuesday."Russia is trying to ethnically cleanse the region by striking opposition-held areas of northern Aleppo in an effort to force local residents to flee," he said.Abu Mahmoud went on to assert that Russia was targeting opposition-held areas north of Aleppo's Azaz district with the aim of helping Daesh while also striking areas southeast of Azaz to help the PYD, the terrorist PKK group's Syrian affiliate.Noting that Russian warplanes had recently carried out airstrikes in the opposition-held Anadan, Hayan, Beyanun, Kafr Hamra, Tel Rifaat, Menagh and Azaz areas, Abu Mahmoud said: "Under Russian air cover, the PYD is advancing eastward".He also said clashes had recently taken place between Syrian opposition forces and the PYD in Aleppo's Menagh district and at the Menagh military airbase.Also on Tuesday, Russian and Syrian warplanes struck targets in the southwestern province of Daraa, according to local sources.The same sources said that Syrian and Russian warplanes had carried out airstrikes in different parts of the province, killing six civilians and injuring dozens of others, including two children.Meanwhile, at least 500 people have been killed on all sides during fighting in Aleppo province since the start of a Syrian army and allied forces offensive began in early February, a war monitor said on Wednesday.The Syrian Observatory for Human Rights, which monitors the war, said this figure included at least 100 civilians. Reuters could not independently confirm the figures.The Syrian army, supported by Russian air strikes, began a push to retake Aleppo and surrounding areas up to the Turkish border at the start of February.Russia first began its air campaign in Syria on Sept. 30 of last year.While Russia claims its campaign is aimed primarily at the Daesh militant group, it has repeatedly targeted civilian areas and the moderate anti-regime opposition groups that control them.Syria has remained locked in a vicious civil war since early 2011, when the regime of Bashar al-Assad cracked down on pro-democracy protests -- which had erupted as part of the "Arab Spring" uprisings -- with unexpected ferocity.Since then, more than 250,000 people in the war-torn country have been killed and more than 10 million displaced, according to UN figures.