At least 43 civilians have been killed in intense Syrian government air strikes on a town near Damascus, a day after the reported execution of a Syrian air force pilot, a monitoring group has said.

Saturday's overnight shelling on Jayrud, 60km northeast of the Syrian capital Damascus, killed at least five women and children, as well as two medical staff.

The UK-based Syrian Observatory for Human Rights said scores of people were also wounded in the strikes, as well as shelling from army posts in the area.

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"There were intense air strikes and multiple targets were hit - residential areas, a medical centre, that is according to activists on the ground," Al Jazeera's Zeina Khodr, reporting from Gaziantep on the Turkish side of the Syria-Turkey border, said.

Khodr said the attacks appeared to be in retaliation for the killing of a Syrian government air force pilot whose warplane had crashed in the area on Friday.

"The pilot managed to eject himself. He was captured but subsequently killed and after his death, the Syrian army promised retaliation and that is exactly what happened."

A rebel spokesman also said the strikes seemed to be in revenge for the pilot's killing.

"The strikes against civilians are in retaliation against the execution of the pilot by Nusra Front," Said Seif al Qalamoni from the Free Syrian Army's Shahid Ahmad Abdo brigade, which operates in Jayrud alongside al-Nusra Front and other groups, told Reuters news agency.

Rebel groups in Jayrud include Jaish al-Islam, Ahrar al-Sham and al-Qaeda affiliate al-Nusra Front.

In a statement, the military had pledged that the killing of its pilot would "not go unpunished".

The Observatory said the raids marked the first bombardment of Jayrud in at least two years.

"Prominent figures in Jayrud have had a local truce with the regime for at least two years, and neither fired on each other," Observatory head Rami Abdel Rahman told the AFP news agency.

The truce had made Jayrud a sanctuary for thousands of civilians fleeing heavy battles nearby.

"The town is heavily populated. Many internally displaced people live there because it was secure due to the truce," said Al Jazeera's Khodr.

Ahrar al-Sham said in an online statement on Saturday it was attacking nearby government positions "in response to warplanes shelling Jayrud".