Boy, 14, seen walking away moments after alleged stabbing at University of Sydney

A 14-year-old boy was seen casually walking away moments after he allegedly stabbed a student at the University of Sydney.

Police and paramedics were called to the Camperdown campus at Parramatta Road about 8.35am today.

First responders arrived and found a 22-year-old stabbed in the neck before taking him to Royal Prince Alfred Hospital in a serious but stable condition.

READ MORE: Two Aussie cities make global top 10

The victim has since been released from hospital.

"We were just sitting in our offices and we heard sirens going off and they locked down some of the buildings in the area," university staff member Bevan de Sousa told 9News.

CCTV footage showed a boy dressed in camouflage walking at a casual pace just two minutes after the alleged stabbing.

He can be seen in the footage cradling his injured hand.

Counter terrorism command assistant commissioner Mark Walton said the 14-year-old boy from the Inner West was arrested after he caught a bus and attended the same hospital for treatment for minor cuts to his hand.

He said the boy was undergoing a mental health assessment and there was no further risk to the community.

"There was a young person who fled the scene dressed in camouflage defence force uniform and a knife was recovered at the scene," he said at a press conference this afternoon.

"The NSW Joint Counter-Terrorism Committee are investigating.

"A motive or ideology, importantly, has not been determined at this time."

Walton, however, said it does not appear that the boy was religiously motivated.

While the boy is believed not to be known to the 22-year-old alleged victim, he is known to police and government agencies.

Forensic police have combed the scene and retrieved a number of items including a backpack which was discarded near a gate.

READ MORE: Sydney council extends, widens free period products in public bathrooms initiative

Walton urged parents and the community to be aware of the risks of young people being radicalised online.

"Everyone should be concerned about this," he said.

"There is a risk of online radicalisation. The internet is toxic and it's very easy for young people especially to self radicalise and move towards violence."

The University of Sydney earlier said it was aware of an incident at the campus and there will be increased security and police presence in the area.

"The safety and wellbeing of our students, staff and members of the community is our priority, and we continue to work with authorities," a spokesperson said.

Readers seeking support can contact Lifeline on 13 11 14 or beyond blue on 1300 22 4636.