At least 20 civilians, including five children, were killed on Monday in Syrian government air strikes on a town in Idlib province in the northwest, a monitoring group said.
The Syrian Observatory for Human Rights said the raids hit a square in the town of Al-Janudiyah, in the west of the province, which is now almost completely controlled by opposition forces.
The Britain-based monitoring group said dozens of people had also been wounded in the strikes, some of them seriously.
Janudiyah has been under opposition control for sometime, but much of Idlib has only recently fallen to a rebel alliance that includes Al-Qaeda affiliate Al-Nusra Front.
Janudiyah lies north of Jisr al-Shughur, which fell on April 25, less than a month after the alliance seized the provincial capital Idlib city.
Government forces now hold only a handful of positions in the province.