Syria and Russia blamed Israel on Monday for early morning airstrikes on a Syrian military base that a conflict monitoring group said killed 14 people, including fighters from Iran.
The strikes appear a day after President Trump warned that President Bashar al-Assad of Syria and his Russian and Iranian backers would have a “big price to pay” after dozens of people were killed near Damascus in what rescue workers said was a chemical attack.
American and French officials denied that their countries had carried out the airstrikes, and an agent for the Israeli military declined to comment.
The airstrikes on Monday hit a Syrian military base known as T4, in the central province of Homs, that has been utilized not only by Syrian forces but also by the Iranian-backed militias that have flocked to the country to assist Mr. Assad’s war effort.
The Russian military said in a statement on Monday that two Israeli F-15 warplanes had launched the strikes, according to the Russian news agency Interfax. The statement said the planes had fired from Lebanese airspace and that Syria’s air defense systems had shot down five of the eight missiles fired.
On Sunday, the National News Agency of Lebanon reported that Israeli surveillance aircraft had been hovering over the country’s northeast, near the border with Syria, for three days.
Israel has struck the T4 air base at least once before, in February, after Israel ambushed what it said was an Iranian drone that had penetrated its airspace. Minutes later, the Israeli military attacked what it called the command-and-control center from which Iran had launched the drone, at the Syrian air base near Palmyra. Syrian antiaircraft missiles then downed one of Israel’s F-16 fighter jets on its way back from the mission.
The first Israeli plane lost under enemy fire in decades, it crashed in northern Israel and prompted a broad wave of Israeli strikes against a dozen Syrian and Iranian targets in Syrian territory.
The war in Syria has sucked in fighters from around the world, as well as global powers including Iran, Israel, Russia, Turkey and the United States, all of which are searching to advance their interests in the Middle East while avoiding direct confrontations with the others.
The latest escalation arrives at a pivotal time for the United States, as Mr. Trump charts the American course in Syria. He said last week that he wanted to withdraw the relatively 2,000 American troops based in eastern Syria, where they are fighting the jihadists of the Islamic State, but his vow to respond to the reported chemical attack on Saturday risks pulling him into Syria in other ways.
The Syrian Observatory for Human Rights, which tracks the conflict in Syria from Britain through contacts on the ground, said that at least 14 people were killed in the strikes on the air base, including fighters from “Syrian, Arab and Asian nationalities.” The group’s director told The Associated Press that most of the dead were Iranians or fighters from Iranian-backed militias.
Throughout seven years of war in Syria, Israel has resisted direct involvement, but it has repeatedly bombed convoys in Syria that were believed to be transporting weapons and other supplies to Hezbollah, the Lebanese militia and political party that is dedicated to Israel’s destruction.
Despite Mr. Trump’s promise to respond to the reported chemical attack in Syria on Saturday, which killed at least 49 people in the Damascus suburb of Douma, it remained unclear what he would do and how it would relate to a broader American policy toward Syria.
After a familiar attack killed scores of people in the village of Khan Sheikhoun in northwestern Syria a year ago, Mr. Trump ordered missile strikes on the Syrian air base where the attacks had originated.
Israel, which shares a frontier with Syria, has also been concerned about the Syrian government’s use of chemical weapons. On Sunday, Yitzchak Yosef, the Sephardi chief rabbi of Israel, condemned the reported chemical attack.
“I have said in the past and I will say it again: What is happening in Syria is genocide of women and children in its cruelest form, utilizing weapons of mass destruction,” he said in a statement. “We have a moral obligation not to keep quiet and to try and stop this massacre.”
While the chief rabbi does not set policy, he does reflect the feelings of many in Israel.