A one-way attack drone struck a US base in Syria on March 23, killing an American contractor, injuring another and wounding five US troops.

That triggered US retaliatory air strikes and exchanges of fire that a Syrian war monitoring group said killed three Syrian troops, 11 Syrian fighters in pro-government militias and five non-Syrian fighters who were aligned with the government.

White House National Security Council spokesperson John Kirby said he was not aware of any additional attacks over the past 36 hours but cautioned, “We’re going to stay vigilant.”

Kirby also referred to President Joe Biden’s remarks on Friday, in which Biden warned Iran that the United States would act forcefully to protect Americans.

“There’s been no change in the US footprint in Syria as a result of what happened the last few days,” Kirby said, adding the mission against Daesh would continue.

“We’re not going to be deterred ... by these attacks from these militant groups.”

Syria’s foreign ministry on Sunday condemned US strikes, saying Washington had lied about what was targeted and pledging to “end the American occupation” of its territory.

Iran’s foreign ministry also condemned the strikes, accusing US forces of targeting “civilian sites.”

US forces first deployed into Syria during the Obama administration’s campaign against Daesh, partnering with a Kurdish-led group called the Syrian Democratic Forces. There are about 900 US troops in Syria, most of them in the east.

Prior to the latest spate of attacks, US troops in Syria had been attacked by Iranian-backed groups about 78 times since the beginning of 2021, according to the US military.

Iran has been a major backer of Syrian President Bashar Assad during Syria’s 12-year conflict.

Iran’s proxy militias, including the Lebanese group Hezbollah and pro-Tehran Iraqi groups, hold sway in swathes of eastern, southern and northern Syria and in suburbs around the capital, Damascus.