Two medics were among at least 31 people killed on Saturday in Syrian government shelling of an opposition-held town northeast of the capital, the Syrian Observatory for Human Rights said.

The bombardment struck the town of Jayrud, 60 kilometres (35 miles) from Damascus, where the army says opposition forces killed a pilot they captured after he was forced to eject on Friday.

Observatory head Rami Abdel Rahman said it was the first bombardment of the town 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," Abdel Rahman told AFP.

He said at least 31 people were killed, including two medics. It was not immediately clear how many of the rest were civilians.

Activists in the town said the head of the local medical centre and several colleagues were killed.

"There have been at least 45 air strikes today. The town's medical centre was hit and its director Amjad al-Danaf was killed," activist Abu Malek al-Jayrudi told AFP via the Internet.

He said the town is home to some 60,000 people and that the bombardment had not stopped since early Saturday.

Syria has been locked in a vicious civil war since early 2011, when the Bashar al-Assad regime cracked down on pro-democracy protests -- which erupted as part of the "Arab Spring" uprisings -- with unexpected ferocity and disproportionate force.

Since then, more than a quarter of a million people have been killed -- and more than 10 million displaced -- throughout the war-battered country, according to the UN.

The Syrian Center for Policy Research, an NGO, however, has put the death toll from the five-year conflict at as high as 470,000.