Syrian security forces and a US-led coalition launched a joint operation on Sunday. The move followed a deadly attack on US troops in central Syria a day earlier.

A Syrian interior ministry official said the forces started a “security campaign” across the Syrian desert. They aimed to track “Daesh sleeper cells” in coordination with the US-led international coalition.

Attack Kills US Troops in Palmyra

The operation came after an attack on Saturday that killed two US soldiers and a civilian interpreter. Syrian authorities called it a “terrorist attack.” Washington said an Islamic State militant carried it out and that security forces later killed the attacker.

The shooting took place in the Palmyra region. Officials said they have arrested three suspects for their alleged involvement.

Arrests Within Security Forces

Syrian authorities said the gunman belonged to the security forces. Officials planned to dismiss him on Sunday because of his “extremist Islamist ideas,” interior ministry spokesman Noureddine al-Baba told state television.

A Syrian security official said authorities arrested “11 members of the general security forces” for questioning after the attack. The official added that the attacker had served “for more than 10 months.” He had postings in several cities before his transfer to Palmyra.

Palmyra is home to UNESCO-listed ancient ruins. Islamic State once controlled the city during its peak expansion.

Leaders React, Trump Warns of Retaliation

Syrian President Ahmed al-Sharaa sent condolences to US President Donald Trump. He expressed Syria’s “solidarity with the victims’ families.”

Trump reacted strongly to the attack. He promised “very serious retaliation.”

A Syrian military official said the shooting happened “during a meeting between Syrian and American officers” at a base in Palmyra. A Pentagon official disputed that claim. The official said the attack occurred “in an area where the Syrian president does not have control.”

Later, the Syrian interior ministry said an Islamic State member had “infiltrated” the meeting before opening fire.

US and Syria Stress Counter-Terrorism Ties

US Envoy to Syria Tom Barrack said the attack “reinforces” the US approach. He said Washington will “enable capable Syrian partners… to hunt down ISIS networks, deny them safe haven, and prevent their resurgence.”

Syrian Foreign Minister Asaad al-Shaibani spoke with US Secretary of State Marco Rubio. He offered condolences and said the attack posed “a new challenge in the fight against terrorism.”

Pentagon spokesman Sean Parnell said the US troops were holding a “key leader engagement” to support counter-terrorism operations when the attack occurred. Trump later said the wounded US troops were “doing well.”

Syrian state media SANA reported that the attack also wounded two Syrian security personnel.

Warnings and Fresh Violence

Interior ministry spokesman Baba said Syrian authorities had issued warnings before the attack. He said there were “prior warnings from the internal security command to allied forces in the desert region.”

“The international coalition forces did not take the Syrian warnings of a possible IS infiltration into consideration,” he said.

On Sunday, gunmen killed four members of the interior ministry’s road security department in Idlib province. Officials did not confirm any link to the Palmyra attack.

ISIS Remains a Threat

Islamic State seized large areas of Syria and Iraq in 2014. The group lost territorial control in Syria five years ago. However, its fighters still operate, especially in desert regions.

Last month, during President Sharaa’s visit to Washington, Syria formally joined the US-led global coalition against Islamic State. This move marked a renewed phase of cooperation between Damascus and Washington.