A US-led coalition air strike killed at least 16 civilians including six women and a child in a village north of so-called Islamic State's Syrian stronghold of Raqqa, the UK-based Syrian Observatory for Human Rights reported.<br/><br/>The IS-held village has been the target of a US-backed alliance of Kurdish and Arab fighters seeking to capture Raqqa. The coalition said, it was checking on the reports of the incident. A spokeswoman for the Kurdish-Arab alliance, the Syria Democratic Forces (SDF), dismissed them.<br/><br/>The initial report of the air strike on al-Heisha, north of Raqqa, came from the anti-IS activist group, Raqqa is being slaughtered silently. It said 23 people had been killed and identified all but four of them. This morning, the Syrian Observatory said 16 had died in the attack.<br/><br/>Research by human rights and monitoring groups indicates that more than 600 civilians could have been killed since coalition air strikes began in Syria two years ago. However, the coalition has admitted responsibility for only 55 civilian deaths in both Syria and neighbouring Iraq between August 2014 and July 2016.