A 14-year-old boy dressed in military clothing is accused of stabbing a 22-year-old student in the neck at the University of Sydney on Tuesday morning, resulting in a campus-wide lockdown.

The student was transported to Royal Prince Alfred Hospital in serious but stable condition. Police in Australia said the victim did not know his attacker.

"A motive or ideology, importantly, has not been determined at this time," said Mark Walton, the acting assistant commissioner for the New South Wales Police.

"The ideology that may be related to this young person's activity is unknown, but I would say it's likely to be categorized as a mixed and unclear ideology. It's certainly not a religiously related ideology," he added.

Walton did, however, express his concern over the increasing evidence of young people being radicalized online, reported Reuters.

"They are embracing violent extremist ideologies and moving towards violence."

The 14-year-old had worn a "camouflage defense force uniform" and left a knife at the scene.

He was apprehended after boarding a bus from the university to a nearby hospital for treatment.

The suspect was being given a mental health assessment, the Associated Press reported.

The attacker was also known to police and government agencies prior to the incident.

The New South Wales Police said there was no ongoing risk and that an investigation is still under way.

In April, a 16-year-old was arrested in connection with the stabbing attack of a bishop during a church service. Police in Australia said he had developed an "extremist ideology."