A journalist walks inside a damaged classroom of the National Legal Training center, a day after gunmen stormed Kabul university in Kabul, Afghanistan on Tuesday. Stunned students demonstrated outside Kabul University on Tuesday after at least 22 people were killed in a brutal, on-campus attack claimed by the Islamic State group. Photo: AFP

Stunned Kabul University students vowed Tuesday to continue their education despite a brutal attack on their campus by the Islamic State group that killed 22 people.

As the first funerals took place, many students returned to see the carnage left after Monday's assault, staging a rally and holding banners that read "Stop Killing Us."

Afghan security forces have been grappling with surging violence that has only worsened in recent months despite the government holding peace talks with the Taliban in Qatar.

"Today, when I came here and saw these classes, I felt like that there was no sign of a university anymore," Sami Ahmadi, who survived the onslaught, told AFP. 

Officials blamed the Taliban for the attack, saying three militants evaded security at the central Kabul campus. 

One blew himself up, they said, while the other two rampaged through the site, shooting students in their classrooms.

The Taliban denied responsibility, however, and the attack was claimed by rival militant group Islamic State, which said two of its fighters carried out the assault.

"Two Islamic State fighters managed to attack a gathering set up by the Afghan government at the Kabul University for the graduation of judges and investigators after completing a course at the university," the group's propaganda arm Amaq said.

Bullet riddled walls and burnt desks and chairs bore testimony to the chaos that sent hundreds of students fleeing onto the streets while others barricaded themselves into rooms.

AFP