KABUL, AFGHANISTAN — More than 30 people were killed and at least 50 others injured after gunmen disguised as doctors attacked a hospital in Afghanistan.

Patients, doctors and hospital staff were among the dead, Reuters reported.

The attack at the Sardar Mohammad Daud Khan military hospital in Kabul began on Wednesday morning when a suicide bomber detonated explosives outside the gates.

At least three gunmen dressed as doctors had taken up positions inside the building. Armed with AK-47 rifles and hand grenades, they began firing.

Members of the security forces rushed to the hospital and a battle ensued that lasted for around six hours. All three gunmen were killed.

ISIS claimed responsibility for the raid.

Afghan President Ashraf Ghani condemned the attack. He said that in all religions, hospitals were regarded as an immune site, according to Reuters.

The military hospital is opposite the U.S. Embassy in Kabul in an area patrolled by heavy security.