President Donald Trump vows "very serious retaliation" after an ISIS gunman killed two U.S. Army soldiers and an interpreter in a Syrian ambush, leaving three other soldiers wounded.

Sgts. William Nathaniel "Nate" Howard and Edgar Torres-Tovar were killed in Syria while they were stationed with the Iowa National Guard.

The shooting happened during a mission by U.S. and Syrian forces in a historic central town near Palmyra on Saturday. President Trump and U.S. military officials attributed the attack to ISIS.

The attack, which took place in the city of Palmyra, comes a year after the fall of Syrian President Bashar al-Assad and the lifting of U.S. sanctions.

Prosecutors will soon indict a young man suspected of membership in ISIS and maintaining contact with a foreign agent linked to the terror group, police announce. The suspect, 20-year-old Kenan Azaiza, resides in the northern Arab town of Daburiyya. He was arrested alongside a second suspect, a resident of Acre, whom police do not name.

The men suspected of attacking a Jewish gathering on Bondi Beach were inspired by the ISIS terror group and spent weeks last month in the Philippines, officials say.

The two men who killed 15 people on Sunday were driven by “Islamic State ideology,” Prime Minister Anthony Albanese told Australia’s public broadcaster.

The black flag of the Islamic State, also known as ISIS, is no longer associated with the sprawling territorial “caliphate” the group once controlled in the Syrian desert. It no longer serves as a banner beckoning Islamist militant recruits from across the globe or as the symbol of an organization with tight operational control over its terrorist plots and media profile.