Israeli warplanes bombed a weapons depot near the Syrian city of Homs on Wednesday, the Syrian Observatory for Human Rights said.
"Israeli planes fired rockets at an arms depot in the industrial zone of Hisyah, south of the city of Homs, the observatory's director, Rami Abdel Rahman, told AFP.
Syrian television reported "an aggression" by Israel in the region, adding that the national army had "responded".
It is not clear whether the target was a weapons depot or a factory or if it was a Syrian facility or belonged to Hezbollah.
Reuters quotes a military commander in the alliance fighting for Damascus that a copper factory was hit. He did not mention any casualties. He also said that an anti-aircraft missile was fired by Syrian forces.
A senior Israeli minister and a military spokeswoman declined to comment to Reuters, but the minister repeated a threat to hit arms shipments to Lebanese Hezbollah.
In recent years, Israel has attacked targets in Syria dozens of times always insisting that arms shipments to Hezbollah is a “red line”.
Israeli Intelligence Minister Israel Katz said, "Israel has acted in the past and it will act in the future to prevent arms smuggling to Hezbollah according to intelligence information that we will have."
Tensions between Israel and Hezbollah have increased this year, as its patron, Iran has consolidated its foothold in Israel.