JERUSALEM — Overnight strikes Thursday on Syrian military sites — which are said to produce chemical weapons and advanced missiles — brought renewed attention to Syria’s chemical weapons, and appear to have been an escalation of Israel’s efforts to prevent its enemies from gaining access to sophisticated weapons.
The Syrian military said Israeli warplanes had struck the sites early Thursday, killing two people near the town of Masyaf in western Syria and causing unspecified material damage.
Israeli officials did not comment on the strike, but a Syrian monitoring group and two former Israeli officials said it had targeted an installation of a government agency that produced chemical weapons and a military base that produced advanced missiles.
The strike came a day after a United Nations commission accused the Syrian government of using chemical weapons in an attack in April that killed dozens in the town of Khan Sheikhoun and flooded clinics with victims gasping for breath.
While many foreign governments and news organizations had previously concluded that Syrian forces were probably behind the attack, the unequivocal condemnation from the United Nations was the most authoritative statement blaming the Syrian government for it.
Continue reading the main storySyria and its ally Russia have claimed that the Syrian government did not use banned munitions and that the attack was carried out by rebels on the ground.
The Syrian government once had large stockpiles of chemical weapons, which it agreed to give up under a 2013 agreement between Russia and the United States. That deal was brokered after Syrian forces were accused of carrying out chemical attacks near Damascus that killed more than 1,000 people.
The agreement was hailed as a diplomatic success by the Obama administration, an achievement now tarred by continued reports of further chemical attacks, indicating that the Syrian government may have hidden some of its chemical stocks or is still producing them.
The Syrian Observatory for Human Rights, which monitors the conflict from Britain through contacts inside Syria, said that the attack on Thursday had hit a branch of the Scientific Studies and Research Center, a government agency that the United States and others have accused of producing chemical weapons.
It also hit a military base nearby where ground-to-ground missiles were kept, the group said.
A BBC report in May named the Masyaf site as one of three places where the agency produced chemical weapons.
Andrew J. Tabler, a Syria expert and fellow at the Washington Institute for Near East Policy, said the United Nations confirmation that Syrian forces had used sarin gas in the April attack would draw attention to the research agency because it would have produced the gas.
But at least as worrying for Israel and other regional powers, he said, was the military base near the Maysaf site that was reported to be producing advanced weapons, particularly missiles capable of carrying chemical weapons. That base was frequented by Iranian forces in Syria who are supporting Mr. Assad’s military, raising fears that weapons made there could be passed to Hezbollah, the Iranian-backed Lebanese militia, or to other Iranian-backed militias.
“The larger context is that the Iranians are in the driver’s seat in Syria,” Mr. Tabler said. “They are playing an unprecedented role.”
Israel has repeatedly hit targets in Syria during the country’s six-year civil war, most of them thought to be armament warehouses or convoys carrying weapons to Hezbollah.
Yaakov Amidror, a former Israeli national security adviser, said the strike on Thursday went a step further. “The big change now is that somebody decided to go to another level of hitting: to the producing stage,” he said in an interview.
As is common with strikes in Syria, Israeli officials declined to comment on it. But Defense Minister Avigdor Lieberman, while insisting that Israel was not seeking “any military adventure in Syria,” said in a radio interview on Thursday that Israel was determined to resist Iran’s influence in the region.
“Everything will be done to prevent the existence of a Shiite corridor from Tehran to Damascus,” he said.
The strike came nine days after Prime Minister Benjamin Netanyahu publicly raised concerns about what he said were Iran’s efforts to produce advanced, precision-guided missiles in Lebanon and Syria.
“Iran is busy turning Syria into a base of military entrenchment,” Mr. Netanyahu said at a news conference last week, “and it wants to use Syria and Lebanon as war fronts against its declared goal to eradicate Israel.”
He added, “This is something Israel cannot accept.”
Previous Israeli strikes in Syria have not led to retaliation by Hezbollah or by the Syrian government, presumably because they prefer to focus on winning the war in Syria without becoming embroiled in a new conflict with Israel.
The United Nations report released on Wednesday said that the attack on Khan Sheikhoun, which prompted President Trump to order cruise missile strikes on a Syrian air base, was just one of at least 20 chemical weapons attacks carried out by Syrian government forces from March 2013 to March 2017.
Amos Yadlin, the executive director of the Institute for National Security Studies at Tel Aviv University, said on Twitter that the strike had hit a factory that “produces the chemical weapons and barrel bombs” — crude explosives dropped from helicopters — “that have killed thousands of Syrian civilians.”
If the attack was conducted by Israel, Mr. Yadlin wrote, it would be both “a commendable and moral action by Israel against the slaughter in Syria.”
An earlier version of this article misspelled the name of Israel’s defense minister. He is Avigdor Lieberman, not Liberman.
