At least 38 people have been killed in air strikes carried out by a US-led coalition in Hasaka province in northeast Syria in the past two days, the Syrian Observatory for Human Rights monitoring group says.
The toll included at least 15 people who were killed when strikes hit a bakery in the city of al-Shadadi near the border with Iraq on Tuesday (local time), the Britain-based Observatory said.
Air raids in at least three other villages killed 15 others on Thursday, including three children, it said. Reuters could not independently confirm the reports.
Al-Shadadi is a logistics hub for the Islamic State group, located on a network of highways and whose capture would isolate Raqqa, the de-facto capital of the hardline group.
The US-led coalition has been hitting Islamic State targets in areas of Syria and Iraq which the group controls, including in Hasaka and Raqqa provinces.
Washington also backs an alliance of Kurdish YPG fighters and other groups fighting against the jihadists on the ground.
The YPG has been the most effective partner against IS in Syria for the US-led coalition, and took swathes of territory from the group last year.
Russia is separately carrying out its own air campaign in Syria, hitting some Islamic State targets, but mostly focused on insurgents fighting Moscow ally President Bashar al-Assad in the west of the war-torn country.