Israel is reported to have carried out a missile strike on a military outpost south of the Syrian capital, Damascus.
Syria's state news agency Sana said two missiles were shot down in the Kiswah area on Tuesday night, and that two civilians were killed in an explosion.
But a monitoring group said the missiles hit an Iranian weapons depot, killing 15 pro-government fighters.
Israel declined to comment. But the reports came after it noted "irregular activity" by Iranian forces in Syria.
The Israeli military placed its troops in the occupied Golan Heights on high alert and urged civilians to prepare bomb shelters.
Israeli Prime Minister Benjamin Netanyahu meanwhile flew to Moscow to discuss Syria with Russian President Vladimir Putin, a key ally of the Syrian government.
Syrian state television broadcast video footage overnight which it said showed air defences intercepting two missiles fired towards Kiswah, about 10km (6 miles) south-west of Damascus.
Sana reported that a man and his wife were killed by an explosion resulting from the interceptions as they drove along the Damascus-Deraa motorway.
A commander in a regional military alliance supporting Syrian President Bashar al-Assad told Reuters news agency that the missiles targeted a Syrian army base.
However, the Syrian Observatory for Human Rights, a UK-based monitoring group, reported that the missiles struck weapons depots and missile launchers belonging to Iran's powerful Revolutionary Guards force.
Eight members of the Revolutionary Guards and several other non-Syrian nationals were among at least 15 pro-government fighters who were killed, it said.