Two 13-year-old girls have been seriously injured and a 16-year-old suspect arrested after an incident at a school in Upper Bavaria, Germany.

Police said a major operation was under way in the area of Welfen-Gymnasium secondary school in the small town of Schongau.

The suspect was carrying a knife as well as a firearm, police said, and they believe they acted alone.

Neither of the girls are in life-threatening condition, but the number of other people involved and the severity of their injuries are currently being clarified, police added.

A police spokeswoman had earlier told AFP news agency it was unclear what weapon had been used in the attack, and declined to confirm reports of a knife attack.

The identity of the suspect is not known and it is unclear if they had links to the school.

The police spokeswoman added the force believe the incident to be a "rampage".

Bavaria's interior minister Joachim Herrmann told German public service broadcaster Bayerischer Rundfunk (BR) he believed the two girls were stabbed. This has not been confirmed by police.

Herrmann added the suspect had previously received psychiatric treatment and said there were unconfirmed indications they were a former student.

A contact point for relatives and parents of students has been set up at a fire station in the town.

According to its website, the school was founded in 1887 and had initially been almost exclusively a girls' school. It has been mixed gender for the last 40 years.