Regime bombardment Sunday killed 12 civilians including three children in an opposition bastion in northwestern Syria, a war monitor said.
Idlib, a region of some three million people, has come under increasing fire by the regime and its ally Russia since late April, despite a months-old international truce deal.
The opposition bastion, which is administered by Syria's former Al-Qaeda affiliate Hayat Tahrir al-Sham, includes most of Idlib province as well as slivers of the adjacent Aleppo, Hama and Latakia provinces.
Seven civilians, including a young girl, were killed in regime artillery fire and air strikes in the north of Hama province, the Syrian Observatory for Human Rights said.
Four more, including a man and his young son, lost their lives when regime aircraft struck near the town of Maaret al-Noman in Idlib province, the Britain-based monitor said.
A third child was killed in regime rocket fire on farmland in Idlib's village of Jadariya.
On Friday and Saturday, strikes by the Damascus government and its Russian ally killed 20 civilians including six children.
More than 540 civilians have been killed in regime and Russian air strikes on northwest Syria since the end of April, the Observatory says.
The United Nations says 25 health facilities in the region have been hit.
Syria's war has killed more than 370,000 people and displaced millions since it started in 2011 with a brutal crackdown on anti-government protests.