At least 20 civilians were killed on Saturday by Syrian government airstrikes and shelling on a rebel-held area near Damascus, where the pilot of a crashed regime warplane was killed the day before, a monitoring group said.
The bombing targeted the area of Jayrude in the Qalamoun region north-east of Damascus, the Syrian Observatory for Human Rights reported.
The regime maintains posts on the outskirts of Jayrude while the centre of the region is jointly controlled by the al-Qaeda-linked al-Nusra Front as well as Islamist rebels Jaish al-Islam and Ahrar al-Sham.
Jaish al-Islam, an alliance of Islamist rebels active in the area, claimed on Friday to have downed the plane.
Later, the monitoring group said the pilot was shot dead by opposition rebels where he was captured.
Responding to news of the death of Lieutenant Colonel Nawras Hassan pilot's slaying, the Syrian army vowed revenged for the "appalling crime" of killing the pilot.
No group has claimed responsibility for the reported killing of the pilot.
Meanwhile a regime helicopter crashed on Saturday in an area controlled by the Islamic State extremist militia. All three officers on board were killed, the monitoring group told dpa.
"We do not know yet the cause of the crash," which took place at the edge of the Sweida province in south-western Syria, watchdog head Rami Abdel-Rahman said.
In recent months, Islamic State has been the target of major attacks in Syria separately launched by Russia-backed regime forces and US-allied rebels.