Israeli air strikes killed 12 pro-Iran fighters near Damascus and in southern Syria early Thursday, the Syrian Observatory for Human Rights said.
Seven foreign fighters were killed in the Kiswa area south of Damascus, where Iranian and pro-Iran foreign fighters are present, the Britain-based war monitor said.
Five Syrian members of a pro-Iranian group were killed in the Ezra area of Daraa province, Observatory head Rami Abdel Rahman said.
A Syrian army source quoted by state news agency SANA said air defences responded to two waves of Israeli strikes after midnight that targeted the Damascus area and then positions in Daraa and the adjacent province of Quneitra.
The source said the attack wounded eight fighters, without elaborating on their rank or nationality.
An Israeli army spokesman contacted by AFP early Thursday declined to comment on the strikes.
Since the beginning of the Syrian conflict in 2011, Israel has carried out repeated strikes against Syrian government forces and their allies, Iran and Lebanese militant group Hezbollah.