Oslo, Mar 19 (IANS): Four staff members were injured on Tuesday when a student attacked them with a knife in a school in the Norwegian capital Oslo, police said.

The student was arrested but the motive was not immediately clear, The Independent daily reported.

The victims suffered bite marks and had been stabbed, Arve Røtterud, a police officer at the school, told a local newspaper.

The four victims, all employees at Brynseng School, were taken to hospital with minor injuries.

An Oslo police official said an investigation had been launched and officers were speaking to witnesses.

"It is a very young boy who is arrested. I can't say anything more about the grade level. He was arrested inside the school," he said.

Police were first called at around 8.30 a.m. local time to reports of an ongoing incident with a student threatening a teacher with a knife.

Police confirmed pupils may have witnessed the incident but no children were harmed.

The school, which opened in 2017 and has more than 800 pupils enrolled, gave no comment.

Local media quoted a text message sent by the head teacher of the school informing parents that the situation was now "calm and under control".

A survey for Norway's educational association last year found around one in five teachers had experienced violence over the previous 12 months.