Syria has arrested five people suspected of having links to the shooting of U.S. and Syrian troops in the central Syrian town of Palmyra on Saturday, the Interior Ministry said on Sunday.

Two U.S. army soldiers and a civilian interpreter were killed by an attacker who targeted a convoy of American and Syrian forces before being shot dead. The Syrian Interior Ministry has described the attacker as a member of the Syrian security forces suspected of sympathizing with ISIS.

Syria has been co-operating with a U.S.-led coalition against ISIS, reaching an agreement last month when President Ahmed al-Sharaa visited the White House.

Syria’s Interior Ministry said its units in Palmyra carried out an operation in co-ordination with “international coalition forces” that resulted in the arrest of five suspects “who were immediately referred for questioning.”

U.S. Secretary of State Marco Rubio discussed the attack by phone with Syrian Foreign Minister Asaad al-Shibani on Sunday. Shibani “offered condolences and reiterated the commitment of the Syrian government to degrade and destroy the shared threat of ISIS,” State Department spokesperson Tommy Pigott said.

Syria’s Interior Ministry said it had assessed the assailant just days before the attack, and concluded he might have extremist views. A decision about his future had been pending.

The U.S.-led coalition has carried out air strikes and ground operations in Syria targeting ISIS suspects in recent months, often with the involvement of Syria’s security forces. Syria last month also carried out a nationwide campaign arresting more than 70 people accused of links to the group.

The United States has troops stationed in northeastern Syria as part of a decade-long effort to fight ISIS, which held swathes of Syria and Iraq from 2014-2019.

Syria’s government is now led by former rebels who toppled leader Bashar al-Assad last year after a 13-year civil war, including members of Syria’s former al-Qaeda branch who broke with the group and clashed with ISIS.