Police have arrested 13 people in Dunedin as student parties get out of hand.

Thirteen people have been arrested in the student quarter since the start of Orientation Week. Of those, only three were confirmed to be students.

Inspector Kelvin Lloyd said police were noticing a large number of non-students partying and causing problems in the area.

HAMISH MCNEILLY/FAIRFAX NZ The remains of a couch on Castle St, Dunedin.

This time, it was at a party where a couch was torched on Tuesday night.

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Campus cop, Senior Constable John Woodhouse, said non-students were becoming an increasing problem in the area.

Hamish McNeilly The remains of a couch on Castle St, Dunedin.

On Friday, police received a complaint from a student that a youth had threatened him with a craft knife.

That youth - a 16-year-old Dunedin boy- was identified by police, but when spoken to an associate threw a bottle at a Campus Watch officer.

"We ran him down and he was found with a knife as well."

The youth would be dealt with by Youth Aid, while his associate would be going to the Dunedin District Court.

Woodhouse said Orientation Week appeared to be a drawcard for non-students, and confirmed some of the traditional student flats were being rented by non-students.

The Fire Service went to Castle St, notorious for student parties, after reports of a couch on fire about 10.56pm Tuesday.

A large party spilled out over the street, with police arresting five people for disorder offences.

Four of those arrested received pre-charge warnings. One was confirmed to be a student.

Firefighters attended other deliberately lit blazes on nearby Leith St North at 12.06am and Howe St at 2.51am.

Orientation Week events at Otago University include the Toga Party on Wednesday.

Police confirmed several large parties had been shutdown prior to the Toga Party.