At least eight people were killed on Wednesday by a Russian airstrike that targeted a market in Syria's northwestern Idlib province, according to a local source."Russian warplanes struck a market in the opposition-held town of Ariha in Idlib, killing eight people and injuring 28 others," Abdel-Karim al-Akhras, a local civil defense official, told Anadolu Agency.He said the attack had caused "severe damage" in the targeted area.According to al-Akhras, efforts were still underway to rescue survivors.Syria has been locked in a vicious civil war since early 2011 when the Assad regime cracked down on pro-democracy protests with unexpected ferocity.Since then, more than 250,000 people have been killed and more than 10 million displaced, according to the UN.On Monday, the U.S. and Russia -- the latter of which has been staging airstrikes against positions held by Assad's opponents since last September -- announced that the Assad regime and opposition forces would cease hostilities starting midnight Saturday.