Syrian forces and a U.S.-led coalition launched an operation against Islamic State group sleeper cells on Sunday, a Syrian interior ministry official said, a day after a deadly attack on U.S. troops in the country.

Two U.S. troops and a civilian interpreter were killed in what the Syrian government described as a “terrorist attack” on Saturday, while Washington said it had been carried out by an Islamic State group (IS) militant who was subsequently killed.

The ministry official, who requested anonymity, said that a “security campaign” across the Syrian desert was tracking “Daesh sleeper cells, in cooperation with the U.S.-led international coalition.”