At least 42 civilians including five children were killed in regime, Russian and US-led coalition air strikes in northern Syria on Wednesday, a monitor said.
Regime air strikes killed 15 civilians in Idlib province, while Russian and regime air strikes killed at least 11 civilians in neighbouring Aleppo province, said the Syrian Observatory for Human Rights.
Seven of those died in regime raids on a bus on the Castello road, a key supply route for the rebels out of the divided provincial capital of Aleppo city, Observatory chief Rami Abdel Rahman said.
Air strikes by the US-led coalition killed a further six civilians in Aleppo's Manbij town and 10 in Raqa city in the province of the same name, both held by the Islamic State militant group, he said.
The international coalition fighting IS group on Wednesday said it had conducted 18 air strikes near Manbij, which is located some 20 miles (30 kilometres) west of the Euphrates river.
Last week, a US-backed Kurdish and Arab alliance launched an assault on IS group north of their de facto Syria capital Raqa, seizing dozens of villages in the north of the Raqa province.
At least 280,000 people have been killed and millions displaced since the Syria war started with the brutal repression of anti-government protests in 2011.