At least twelve people died and 26 were injured after terrorists attacked the American University in Kabul, Afghanistan on Wednesday. Armed troops cordoned off the area soon after explosions and gunfire began at the institution, reported AFP. Several students and teachers were trapped inside their classrooms after the attack started.

Interior ministry spokesman Sediq Sediqqi said officials were not sure how many militants were involved in the attack, and that security forces had started clearing operations soon after it began. On Thursday morning, Afghan officials said all attackers had been killed.

No group has claimed the incident yet, though it comes as Taliban militants step up their summer fighting season against the Kabul government.