'US coalition raids' kill civilians in northern Syria
"The raids hit the village of al-Matab after midnight and were likely carried out by the coalition," said Rami Abdel Rahman of the Syrian Observatory for Human Rights.
Al-Matab lies near a key road linking Raqqa - IS' de facto capital - to Deir Az-Zour city, the capital of the adjacent oil-rich province.
On Monday, fighters from the US-backed Syrian Democratic Forces cut off that route in a bid to encircle the militants in Raqqa.
The US-led coalition has been backing the SDF's drive for Raqqa with air power and hundreds of special operations forces as advisers.
Abdel Rahman said SDF fighters advancing on IS militants in al-Matab, which lies about 55 kilometres (35 miles) southeast of Raqqa.
The SDF - an alliance of Kurdish and Arab fighters - launched its offensive for Raqqa in early November and has since seized swathes of territory in northern Syria.
But it is despised by Ankara, who condemns the group's dominant component - the Kurdish People's Protection Units (YPG) - as "terrorists" because of its links to an outlawed Kurdish militia in Turkey.