At least 18 people were killed on Sunday by a blast that targeted a rebels' position in Idlib, Syria, a monitor group said.Civilians were among those killed and wounded by the car bomb that targeted a position of Agnad al-Caucaus rebel group, Xinhua reported.The Syrian Observatory for Human Rights said the blast was heavy, stopping short of giving details on the number of civilians among the killed militants.The Syrian army has been on a wide-scale offensive in the southern countryside of Idlib, capturing tens of towns and villages over the past two months.The recent military victory was achieved on Sunday when the Syrian army captured the strategic town of Sinjar, which enables the government forces to advance toward capturing the key airbase of Abu al-Duhur.Idlib has emerged as the main destination of the rebel groups, which have evacuated several positions across Syria after surrendering to the Syrian army.The area has become a home to several rebel groups from different affiliations, some of which are supported by Turkey, while others, such as the Nusra Front, are designated as terrorist groups.