Overnight Saturday, a string of explosions at a military airport near the Syrian capital reportedly killed two regime fighters and injured 11 others.
The report of the attack came at a time when Iranian Foreign Minister Mohammad Javad Zarif was visiting Damascus for talks with senior Syrian officials, in advance of the battle for Idlib in the northwest of the country, which is considered the last major rebel enclave.
Assad's forces, backed by military support from Russian Federation and Iran, have recaptured major cities in recent years, often involving agreements with both opposition fighters and civilians that allowed them to flee to Idlib.
State media on Sunday cited a military source as saying there was no "Israeli aggression" directed at the airbase and mentioned no casualties.
The Britain-based Syrian Observatory for Human Rights said the blasts that rocked Damascus resulted in several explosions in a weapons depot inside the airport.
He could not specify their nationalities or whether they belonged to militias or government forces.
Iran's official IRNA news agency quoted an unnamed Syria-based Iranian military official as saying an explosion was caused by an electrical short circuit.
"The explosions heard were due to an explosion at a munitions deposit close to the airport which was due to an electrical short circuit", the source said.
Several strikes against Syrian government or allied forces have in the past been attributed to U.S. forces, which were deployed with the declared goal of fighting the Islamic State (IS) group. Israel rarely acknowledges such strikes, but has recently targeted suspected Iranian posts inside Syria.
Sunday saw a report in Syria about an aerial strike near the Al Mezzeh military airport in Damascus, which was attributed to Israel. Israel has grown nervous of Iran's growing presence in Syria and threatened to prevent a build-up of pro-Iranian forces near its frontiers with Syria.
More than seven years since Syria's conflict began, regime forces have managed to retake entire regions from rebels and jihadists and now control almost two-thirds of the country.
Syrian troops are supported military by their Russian and Iranian allies, Tehran-backed Hezbollah fighters as well as Iraqi, Iranian and Afghan militiamen.