Syrian President Bashar Assad and the Russian defense ministry accused Israel of launching a predawn missile strike on Monday on a Syrian air base, killing 14 people, including numerous Iranian military personnel.

Israeli officials have refused to comment.

Both the United States and France officially denied any part in the strike, which occurred just after the countries warned they would retaliate against Assad’s regime due to his use of chemical weapons against the residents of the town of Douma on Saturday. Initially, Syria called the attack “an American aggression,” but shifted the accusations to Israel following America’s official denial.

The airstrike was reportedly conducted at the Tiyas or T-4 air-force base outside Palmyra in central Syria.

Russia claimed that the targeting took place just before 4 a.m. by two Israeli F-15 fighter jets, which launched eight missiles from Lebanese airspace, five of which Russia claims were intercepted by its air defenses.

Israel has attacked the site, home to an Iranian drone program, once before on Feb. 10, when an Iranian operator flew on Iranian-made drone from the base into Israeli territory.