The attack led to an armed clash between the gunmen and the police, which killed at least 19 and wounded 22.
“The enemies of Afghanistan, the enemies of education [...] have entered Kabul University,” Tariq Arian, a spokesman for the ministry of interior was quoted as saying by Dawn.
“The security forces are in the area trying to control the situation. They are advancing carefully to prevent any harm to the students.”
The Iranian publishers have reportedly been taken back to the Iranian embassy.
The Taliban said they were not involved.
Hamid Obaidi, a spokesman for the ministry of higher education, told AFP that gunfire erupted when government officials were expected to arrive for the opening of the book event.
Arian said several people had been rescued from the university campus.
Masooma Jafari, a deputy spokeswoman for the health ministry, told AFP that eight people, including students and teachers, had been taken to hospital.
Students spoke of chaos and confusion as gunfire erupted. “We were studying inside our classrooms when suddenly we heard a burst of gunfire inside the university,” said student Fraidoon Ahmadi, 23.
“Some university students have fled [...] it is chaotic and students are terrified,” he added. Ahmadi said he and several other students were besieged for more than two hours before being rescued.
“We were very scared and we thought it could be the last day of our lives [...] boys and girls were shouting, praying and crying for help.
“I have no words to express how we survived today's attack by gunmen on our university,” he said, adding that there were about 800 students in the social sciences faculty itself where he studied.
Last week at least 24 people, mostly students, were killed in a suicide attack on an educational center in western Kabul.
MR/PR