“Shocking news from Kongsberg, Norway.
My thoughts are with the victims and those who have lost their loved ones.
We must work together to confront hatred and violence, ”Stoltenberg wrote.
German Foreign Minister Heiko Maas also wrote a post of condolences.
He condemned the "brutal attack" and expressed condolences to the families of the victims.
An attack by a man with a bow and arrow in the Norwegian town of Kongsberg killed five people.
The attacker was detained.
The Norwegian police called the attack in Kongsberg a terrorist attack.