Police in Oslo have cordoned off a large section of a busy street after finding what they said was a "bomb-like" device.
The official police Twitter account said a man had been arrested and police chief Vidar Pedersen said bomb disposal experts were on the scene in the Norwegian capital.
Police swept through the area to remove people from bars and restaurants.
"Every restaurant was being closed," said 23-year-old Malin Myrvold, who witnessed the scene from a fourth-storey window.
"You could see cops in heavy armour going in every store and restaurant.
"We were trying to see what was going on. The police were screaming at us to get back inside and stay where we were."
Norway was put on high alert after the lorry attack in neighbouring Sweden on Friday that killed four people and injured 15 in the capital Stockholm.
It is unclear whether the arrested suspect, a 39-year-old native of Uzbekistan, was also a Swedish citizen or resident or even how long he had been in the country.
AP
