Two students were killed and 14 injured in an attack at the American University of Afganistan in Kabul, Reuters reported citing the head of Kabul hospitals.
Many trapped students were tweeting desperate messages for help.
No militant group has so far claimed responsibility for the attack, which comes as the Taliban step up their summer fighting season against the Western-backed Kabul government.
The Italian-run Emergency Hospital in Kabul tweeted that at least five wounded people had been brought to the facility for treatment.
The management of the elite AmericanUniversity of Afghanistan, which opened in 2006 and enrols more than 1,700 students, was not immediately reachable for comment.
The private university is usually packed with students in the evening, many of them working professionals doing part-time courses at the facility..