KABUL, Afghanistan (AP) — The U.S. Embassy in Afghanistan says three doctors killed by an Afghan security guard at a Kabul hospital are American citizens.

Thursday's shooting at Cure International Hospital in western Kabul was the latest attack on foreign civilians in the Afghan capital this year.

The embassy says on Twitter: "With great sadness we confirm that three Americans were killed in the attack on Cure hospital."

The motive for the attack was unclear.