Britain-based Syrian Observatory for Human Rights says seven children are among those killed in air raids in Idlib and Hama provinces. Separately, a suicide bomber killed six regime soldiers in southern Daraa province.
Regime and Russian air strikes on Saturday killed 15 civilians, more than half of them children, in northwestern Syria where ramped up attacks by the two allies have claimed hundreds of lives since April, a war monitor said.
In a separate incident in southern Daraa province, the Syrian Observatory for Human Rights (or SOHR) said a suicide bomber killed six regime soldiers.
In the Idlib town of Ariha, seven children were among 11 civilians killed in Syrian air strikes that targeted two residential buildings and also wounded 28 other people, said the SOHR.
Russi air strikes on northern Hama province that hit an ambulance killed three rescuers while another child died in Syrian regime bombardment elsewhere in the Idlib region, the monitor said.
One of the dead was a small boy who was found under the rubble by White Helmets rescuers, his face bloodied and his body covered in white dust, a photographer who works with AFP news agency said from the scene.
He also witnessed rescuers digging through the rubble of a collapsed roof for more victims, while a member of the White Helmets moved the body of a young man into the back of a pickup truck
Bomber kills six regime troops
Also on Saturday, a suicide bomber killed six regime soldiers in the southern province of Daraa, in a rare deadly attack against the cradle of the uprising that sparked Syria's war, SOHR said.
The bomber, who was riding a motorcycle, blew himself up at a military checkpoint killing the six soldiers and wounding several other people, the monitor said.
Syria's regime-run news agency SANA also reported a suicide bombing but said it happened during an "army raid" that targeted "terrorists", a term used by authorities to describe rebels and militants.
Buffer zone deal violation
Idlib and parts of the neighbouring provinces of Aleppo, Hama, and Latakia are under the control of Hayat Tahrir al Sham, a militant group led by Syria's former al Qaeda affiliate, and other rebel groups.
The region is supposed to be protected from a massive regime offensive by a September buffer zone deal, but it has come under increasing bombardment by the regime and its Russian ally over the past three months.
Over 100 civilians killed in 10 days
The latest bombardment came a day after the UN condemned attacks at civilians, saying over 100 people have been killed in the past 10 days.
Air strikes by the Syrian regime and its allies on schools, hospitals, markets and bakeries have killed at least 103 civilians in the past 10 days, including 26 children, UN human rights chief Michelle Bachelet said in a statement on Friday.
Over the past three months, the offensive has driven hundreds of thousands of people from their homes or temporary shelters to seek refuge near the border with Turkey and has killed hundreds of civilians, according to war monitoring groups.
Both the Syrian regime and its Russian ally, whose air power has been critical to Damascus' military gains in recent years, deny targeting civilians or civilian infrastructure.
The war in Syria has killed more than 400,000 people and displaced millions since it started in 2011 with a brutal crackdown on anti-regime protests.