At least two members of Syria's pro-government forces were killed overnight in a series of explosions at a military airport near the country's capital, a monitoring group said on Sunday.
Syrian state media also reported the blasts at the Mazzeh airbase, on the western outskirts of Damascus, but did not mention casualties.
The Syrian Observatory for Human Rights war monitor said Mazzeh was hit by a "possible Israeli missile, which hit a munitions store setting off successive explosions".
"It left two pro-regime fighters dead and wounded another 11, some of them in critical condition," Observatory chief Rami Abdel Rahman said.
He could not specify their nationalities or whether they belonged to militias or government forces.
An Israeli military spokeswoman declined to comment on Sunday.
AFP correspondents in Damascus heard several blasts overnight, one of which lit up the sky in a deep red hue, but reported calm on Sunday morning.
A Syrian military source said the Mazzeh airbase "was not the target of Israeli aggression", according to the official Sana news agency.
"The explosions heard were due to an explosion at a munitions dump close to the airport which was due to an electrical short circuit," the source said.
The Mazzeh airbase houses Syrian Air Force intelligence personnel, and early last year the Syrian government accused its neighbour Israel of bombing the base.
Israel has sought to avoid direct involvement in the conflict, but has acknowledged carrying out dozens of air strikes in Syria to stop what it said were deliveries of advanced weaponry to its Lebanese enemy Hezbollah.
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It has also pledged to prevent its arch foe Iran from entrenching itself militarily in Syria, and a series of strikes that have killed Iranians in Syria have been attributed to Israel.
This week, Israel reiterated its threat to hit Iranian military targets in Syria.
"The IDF will continue to take strong and determined action against Iran's attempts to station forces and advanced weapons systems in Syria," Prime Minister Benjamin Netanyahu said.
In July, Syria accused Israel of bombing a military post in the northern province of Aleppo, where at least nine pro-regime fighters were killed, according to the Observatory.
More than seven years since Syria's conflict began, regime forces have managed to retake entire regions from rebels and extremists and now control nearly two thirds of the country.
Syrian troops are supported militarily by their Russian and Iranian allies, Tehran-backed Hezbollah fighters as well as Iraqi, Iranian and Afghan militiamen.