Two U.S. soldiers and an American interpreter were killed in an ISIS attack near Palmyra, Syria, prompting President Donald Trump and the Pentagon to promise swift retaliation as the investigation continues.

Two US soldiers and a US civilian interpreter have been been killed in Syria in an ambush by a lone Islamic State gunman, the US military has said. The Pentagon said three other service members were injured in the attack, during which the gunman was "engaged and killed".

A pair of Iowa National Guard soldiers were killed during a recent attack in Syria, the governor's office announced during a press conference. Iowa National Guard Major General Stephen Osborn said the two unnamed soldiers were killed Saturday, Dec. 13, by a "lone ISIS gunman in Syria."

The U.S. currently has hundreds of troops deployed in eastern Syria as part of a coalition fighting the Islamic State group.