Newcastle police yesterday charged the teens, aged 16 and 17, with armed robbery and extortion after a 22-year-old woman was robbed while walking through Callaghan Campus on Thursday night.

Police said the student from China was held up at knifepoint at 9.30pm by two youths on push bikes who stole her bag including her mobile phone.

Police said teens rang a friend of the woman early yesterday and demanded cash or the woman would be hurt.

The pair was arrested in Shortland yesterday after police placed a parcel in a public area.

There have been at least 11 other cases of overseas students being bashed, robbed or held up at knifepoint around Callaghan campus since mid-January as well as cases of Australian students being attacked.

Police have made six arrests over the recent spate, including a 12-year-old boy.

University of Newcastle denied claims the campus security budget had been halved but reinstated a night-time shuttle bus service in response to the recent incidents.

Acting Vice Chancellor Sue Gould released details of its security funding this week to scotch claims by the Newcastle University Students Association it had cut the budget in 2009.

Security spending has increased from $1.4 million in 2008 to $1.6 million in 2009.