Three other people were lightly injured during the incident, and the attacker fled before police arrived on the scene.

"We have information that this man is dangerous, that he is aggressive and, shall we say, psychologically disturbed," senior regional police official Ravi Landolt told reporters.

Police said the assault was not a terrorist attack but more likely due to some grievance the suspect had against the health insurance company.

The suspect apparently lives mostly in woods, Mr Landolt said.