A group monitoring the confilct in Syria says goverment airstrikes have killed at least 37 civilians in an area controlled by Islamic State fighters.
The Syrian Observatory for Human Rights says seven children and two women were among those killed in the attack on Al-Bab and the nearby town of Qabaseen.
The British-based group had previously put the death toll from the Thursday airstrikes at 21.
The area, northeast of Aleppo, is controlled by Islamic State extremists and has been the target of repeated government bombings.
A U.S.-led campaign of airstrikes is also attempting to drive the rebels out of their strongholds in northeast Syria and northern Iraq.
Earlier this week, Islamic State militants captured a Jordanian pilot whose coalition fighter jet went down near the Syrian town of Raqqa.
The U.S. and Jordanian militaries have acknowledged the plane crashed, but dispute militant claims that brought it down.