Two US soldiers and a civilian interpreter were killed in central Syria after an ambush carried out by a lone Islamic State gunman, the US military said.
US Central Command said three other American service members were wounded in the attack. The gunman was later engaged and killed by partner forces.
President Donald Trump described the incident as an ISIS attack against both the United States and Syria, warning that there would be “very serious retaliation.” He said the three wounded Americans were recovering and offered condolences to the families of those killed.
The ambush took place near Palmyra while US personnel were conducting a meeting with local leaders, according to the Pentagon. A defence official said the attack occurred in an area not fully under the control of the Syrian government.
The identities of those killed are being withheld for 24 hours until their next of kin are notified, US Central Command said.
ISIS has not claimed responsibility for the attack. The Syrian Observatory for Human Rights said the attacker was linked to Syrian security forces, a claim not confirmed by US officials.
US Defence Secretary Pete Hegseth said anyone who targets Americans would be relentlessly pursued, adding that the United States remains committed to defeating ISIS alongside its partners.
Syria recently joined the US-led international coalition against ISIS. Last month, Syrian President Ahmed al-Sharaa met Trump at the White House, describing the visit as the beginning of a new phase in relations between the two countries.
The US-led coalition was formed in 2014 to combat ISIS in Syria and Iraq and continues operations to prevent the group’s resurgence.