Israel fired several missiles early on Monday targeting areas near the Syrian capital, Syria's state news agency reported. An opposition war-monitoring group said the strikes killed six Iran-backed fighters.
Syria's army earlier said the country's air defenses "repelled Israeli aggression" over Damascus. The SANA news agency claimed that Syrian air defenses shot down most of the missiles, which it said were fired from the Golan Heights.
The Britain-based Syrian Observatory for Human Rights, an opposition war monitor with a network of activists on the ground, said the strikes hit positions of the Syrian army's Fourth Division in the mountains near the highway that links Damascus with the Lebanese capital of Beirut.
The Observatory said that of the six Iran-backed fighters killed, four were near the Damascus-Beirut highway and two in Kisweh. Weapons depots were also struck in both areas, it added.
A Syrian military defector said another strike hit Syrian army positions in Kisweh, almost 14 km (8.7 miles) south of the capital, in a sprawling area where Iranian-backed militias have a dominant presence.
Witnesses heard large explosions on the southern edge of Damascus, an area where Iranian-backed militias are entrenched, residents said.
Israel's military did not immediately comment on the latest strike, but its senior military officials have acknowledged the escalating attacks inside Syria aimed to end Tehran's entrenched military presence in Syria.
Israel's Defense Force chief of staff, Aviv Kochavi, said at the end of last year that his country's missile strikes had "slowed down Iran's entrenchment in Syria," hitting more than 500 targets in 2020.
Western intelligence sources say Iran's military influence has expanded in Syria in recent years, prompting Israel to escalate its campaign to prevent its arch rival from establishing a major military foothold along its border.
Iran's proxy militias, led by Lebanon's Hezbollah, now hold sway over vast areas in eastern, southern and northwestern Syria, as well as several suburbs around Damascus. They also control Lebanese-Syrian border areas.
Israel, which in the last two months staged some of its biggest strikes yet inside Syria, has concentrated on Al Bukamal, the Syrian city that controls the border checkpoint on the main Baghdad-Damascus highway.
The widening military campaign was part of a so-called "campaign within wars", which, according to Israeli generals and regional intelligence sources, have been tacitly approved by the United States.
The operations that aim to prevent Tehran from changing the balance of power in Syria in its favour have gradually eroded Iran's extensive military power without triggering a major increase in hostilities, regional intelligence sources say.