Norwegian police have detonated an explosive device found outside a busy underground station in central Oslo.
Officers evacuated late-night bars and restaurants near the Groenland underground station as bomb disposal experts rushed to the scene.
Authorities later said the device was neutralised and a suspect arrested.
"The noise from the blast was louder than our explosives themselves would cause," a police spokesman said, while adding that further investigation would be conducted at the scene.
The device had appeared to be capable of causing only a limited amount of damage, the police said earlier.
Police declined to give information about the suspect.
"Every restaurant was being closed," Malin Myrvold, who witnessed the scene from a fourth-storey window, told the Associated Press.
"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 neighbouring Sweden suffered a truck attack in the capital Stockholm that killed four people and injured 15.
The suspect in Friday's attack, a 39-year-old native of Uzbekistan, has been arrested.
