Afghan police arrive at the site of an attack at Kabul University on Monday. AP

At least 19 people including students were killed and 22 others injured after a six-hour-long gun battle between security forces and three militants at Kabul University came to an end, Afghanistan's interior ministry said later on Monday.

"The attack is over, but sadly 19 people have been killed and 22 more wounded," interior ministry spokesman Tariq Arian said on Twitter.

This was the second attack on an educational institution in the Afghan capital in just over a week, officials and witnesses said.

Kabul police spokesman Ferdaws Faramerz said most of those killed were students.

A student, wounded after gunmen stormed Kabul University, arrives in an ambulance to Isteqlal Hospital. AFP

Photos shared by a senior government official showed students lying dead in classrooms, some next to their books. One student appeared to have been shot as they were climbing out of a window.

"They were shooting at every student they saw ... they even shot at the students who were running away," witness Fathullah Moradi said.

"Three attackers were involved. One of them blew up his explosives at the beginning, two were brought down by the security forces," Arian said.

The Taliban said they were not involved in Monday's incident at Kabul University, but several education centres have been attacked over the years by extremist groups such as Daesh.

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Hamid Obaidi, a spokesman for the ministry of higher education, said the attack started when government officials were arriving for the opening of an Iranian book fair organised at the campus.

Students spoke of chaos and confusion. "We were studying inside our classrooms when suddenly we heard a burst of gunfire inside the university," said Fraidoon Ahmadi, 23, adding that 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."

School children walk along a road near Kabul University. AFP

About 800 students were in the social sciences faculty where he was studying.

"I have no words to express how we survived today's attack by gunmen on our university," he added.

Last week at least 24 people, mostly students, were killed in a suicide attack on an educational centre in western Kabul that was claimed by Daesh.