Israel struck an arms supply hub operated by the Lebanese group Hezbollah near Damascus airport on Thursday, Syrian rebel and regional sources said, targeting weapons regularly sent from Iran via commercial and military cargo planes, Reuters reported.
Video carried on Lebanese TV and shared on social media sites showed the pre-dawn airstrikes caused a fire around the airport east of Damascus, suggesting fuel sources or weapons containing explosives were hit.
Israel does not usually comment on any action it takes in Syria or the wider region. But Intelligence Minister Israel Katz, speaking to Army Radio from the United States, appeared to confirm Israel's involvement.
"The incident in Syria corresponds completely with Israel's policy to act to prevent Iran's smuggling of advanced weapons via Syria to Hezbollah," he said.
"The prime minister has said that whenever we receive intelligence that indicated an intention to transfer advanced weapons to Hezbollah, we will act."
An Israeli military spokeswoman said: "We can't comment on such reports."
Two senior rebel sources operating in the Damascus area cited their monitors in the eastern outskirts of the Syrian capital as saying five strikes had hit an ammunition depot used by Iran-backed militias.
Lebanon's al-Manar television, which is affiliated with Hezbollah, said early indications were that the strikes hit warehouses and fuel tanks and had caused only material damage and no human casualties.
Russia and Iran back Assad
Syrian President Bashar al-Assad is backed in his six-year-old civil war by Russia, Iran and regional Shi'ite militias including Hezbollah, a close ally of Tehran and enemy of Israel.
Syrian military defectors familiar with the airport say it plays a major role as a conduit for arms from Tehran.
Alongside military planes, there are a number of commercial cargo aircraft that fly regularly from Iran to refurbish arms supplies quickly to Hezbollah and other groups. The flights go directly from Iran to Syria, passing over Iraqi airspace.
"The Assad regime uses civil aviation to transport weapons and ammunition and get fighters from Iran," said Wael Alwan, a senior official in the Failaq al Rahman rebel group that operates from a stronghold on the outskirts of Damascus.
Alongside weapons, hundreds of Shi'ite militia fighters from Iraq and Iran are also flown into Syria from Damascus international airport. Intelligence sources put their numbers at from 10,000 to 20,000 and say they play a significant role in military campaigns launched by the Syrian army.
Israel has largely kept out the war in Syria, but officials have consistently referred to two red lines that have prompted a military response in the past: any supply of advanced weaponry to Hezbollah or the establishment of "launch sites" for attacks on Israel from the Golan Heights region.
Speaking in Moscow on Wednesday, where he was attending a security conference, Israeli Defence Minister Avigdor Lieberman reiterated that Israel "will not allow Iranian and Hezbollah forces to be amassed on the Golan Heights border".
During his visit, Lieberman held talks with Russian Defence Minister Sergei Shoigu and Foreign Minister Sergei Lavrov, as part of efforts by Israel to coordinate with Moscow on actions in Syria and avoid the risk of confrontation.
A statement from the Defence Ministry said Lieberman had expressed concern to the Russian ministers over "Iranian activity in Syria and the Iranian use of Syrian soil as a base for arms smuggling to Hezbollah in Lebanon".
A Western diplomat said the airstrikes sent a strong political message to Iran, effectively saying it could no longer use Iraqi and Syrian airspace to resupply its proxies in Syria with impunity.
Speaking to Reuters in an interview in Washington on Wednesday, Katz, the intelligence minister, said he was seeking an understanding with the Trump administration that Iran not be allowed to establish a permanent military foothold in Syria.
Israeli officials have estimated that Iran commands around 25,000 fighters in Syria, including members of its own Revolutionary Guard, Shi'ite militants from Iraq and recruits from Afghanistan and Pakistan.