Syrian government air strikes on Tuesday killed at least 39 people, more than half of them civilians, in two main battlegrounds in the north of the country, a monitor said.

"The Syrian Observatory for Human Rights has documented the deaths of at least 27 people... in air strikes targeting the outskirts of Tal Hamis," said the Britain-based organisation.

Speaking to AFP, Observatory director Rami Abdel Rahman said nine of those killed had been identified by his group as civilians.

"More of the dead may be civilians too, but we have not yet been able to confirm that," Abdel Rahman said.

He added that Tal Hamis, situated in Hasakeh province which borders Iraq and which is home to a sizeable Kurdish population, is under the control of the Islamic State jihadist group.

"There are daily air regime and (US-led) coalition air strikes against IS positions in Hasakeh," said Abdel Rahman.

Tuesday's bombing was especially deadly because it struck a cattle market.

"Some of the bodies were so mutilated by the strikes that people couldn't tell the human from the animal remains," said Abdel Rahman.

Earlier Tuesday, the Observatory reported a string of air strikes against the town of Saraqeb and the village of Sheikh Mustafa in the northwestern province of Idlib.

Eleven civilians were killed in Saraqeb, and another man died in Sheikh Mustafa, according to the group, which relies on a broad network of activists and doctors for its reports.

Both towns are under jihadist control, though all of Tuesday's casualties there were civilians.

Most of Idlib's countryside is out of government control, but its capital remains in regime hands.

In November, Al-Qaeda affiliate Al-Nusra Front expelled Western-backed rebels from their Idlib positions.

The province's countryside was among the first areas the government lost in the nearly four year conflict.

The conflict began when forces loyal to President Bashar al-Assad launched a brutal crackdown on peaceful pro-reform protests in March 2011 that triggered a complex, multi-sided civil war.

It has cost the lives of more than 200,000 people and forced half the country's population to flee their homes.