A string of powerful blasts from the direction of a military airport in Damascus lit up the skies and shook the capital city in the early hours of the morning, residents and regime TV reported.
Syrian regime media said loud blasts coming from an airbase early on Sunday were from an explosion at an ammunition dump caused by an electrical problem, but an official in the regional alliance backing Damascus said they were from Israeli strikes.
The regime media cited a military source as saying there was no "Israeli aggression" directed at the al Mezzah airbase near Damascus, after the sound of explosions was heard across the Syrian capital.
The official had said the blasts were caused by Israeli missile fire from across the Golan Heights frontier between the two countries and by Syrian air defences responding.
A war monitor, the Syrian Observatory for Human Rights, also attributed the blasts to Israeli strikes, which it said caused deaths and injuries.
Israel has previously acknowledged having carried out air strikes in Syria aimed at degrading the capacity of Iran and its allies, including Lebanon's Shia Hezbollah group, which are backing Assad in the country's seven-year civil war.
There was no immediate comment from Israel on reports of Sunday's blasts or that it was behind them.
In May, it said it attacked nearly all of Iran’s military infrastructure in Syria after Iranian forces fired rockets at Israeli-held territory for the first time in the most extensive military exchange ever between the two adversaries.