The Syrian army said Israel targeted a military site in Hama province early on Thursday which a war monitor said could be linked to chemical weapons production.
The air strike killed two soldiers and caused damage near the town of Masyaf, an army statement said. It warned of the “dangerous repercussions of this aggressive action to the security and stability of the region”.
The Syrian Observatory for Human Rights, which monitors the war, said the strike hit a Scientific Studies and Research Centre facility, an agency which the United States describes as Syria’s chemical weapons manufacturer.
The strike took place the morning after UN investigators said the Syrian government was responsible for a sarin poison gas attack in April.
Syria’s government denies using chemical weapons and in 2013 it promised to surrender its chemical weapons programme, which it says it has done.
The Observatory said strikes also hit a military camp next to the centre that was used to store ground-to-ground rockets and where personnel of Iran and its ally, the Lebanese Hezbollah group, had been seen more than once.
An Israeli army spokeswoman declined to discuss reports of a strike in Syria. Israeli officials have in the past admitted that Israel has repeatedly struck weapons shipments believed to be bound for the Iranian-backed Hezbollah, an ally of Syrian President Bashar al-Assad, without specifying which ones.
In an interview in Haaretz last month upon his retirement, former Israeli air force chief Amir Eshel said Israel had struck Syrian and Hezbollah arms convoys nearly 100 times in the past five years.
Israel sees a red line in the shipment to Hezbollah of anti-aircraft missiles, precision ground-ground missiles and non-conventional (chemical) weapons.
Hezbollah and Israel fought a brief war in 2006 and both have suggested that any new conflict between them could be on a larger scale than that one, which led to the deaths of more than 1,300 people.
Hezbollah has been one of Assad’s most important allies in the war and last month its leader Sayyed Hassan Nasrallah said he had recently travelled to Damascus to meet the Syrian president.
Israel is conducting military exercises in the north of the country near the border with Lebanon.
Yaakov Amidror, a retired Israeli general and former national security adviser, told reporters that he assumed Thursday’s strike was linked to Nasrallah’s visited to Damascus.
“Weapons systems have been transferred from this organisation (the Scientific Studies and Research Centre) into the hands of Hezbollah during the years,” he said.
In May, an official in the military alliance backing Assad said that Hezbollah drew a distinction between Israel striking its positions in Syria and at home in Lebanon. “If Israel strikes Hezbollah in Lebanon, definitely it will respond,” the official said.
The Syrian army statement said the Israeli strike, which it said took place at 2.42am (23.42 GMT) from inside Lebanese airspace, had been made in support of Islamic State.
Jets flying over Lebanon overnight broke the sound barrier and Lebanese media reported thatIsraeli warplanes had breached Lebanese airspace.
The Observatory reported a total of seven people killed and wounded in the strike.
Amos Yadlin, a former head of Israeli military intelligence, said the reported attack was not routine and targeted a Syrian military scientific centre.
“The factory that was targeted in Masyaf produces the chemical weapons and barrel bombs that have killed thousands of Syrian civilians,” Yadlin said in a tweet.
The strike sent a message that Israel would not let Syria produce strategic weapons, would enforce its own red lines, and would not be hampered by Russian air defence systems in Syria, he added.
The UN Commission of Inquiry on Syria said on Wednesday that a government jet dropped sarin on Khan Sheikhoun in Idlib province in April, killing more than 80 civilians, and that government forces were behind at least 27 chemical attacks.
Israeli officials have also previously said that Russia, another Assad ally, and Israel maintain regular contacts to coordinate military action in Syria.
The reported attack also took place on the 10th anniversary of Israel‘s destruction of Syria’s nuclear reactor.