A bomb ripped through Oslo's central government district Friday and a gunmen dressed as a policeman then opened fire at a youth camp on a nearby island, killing 17 people altogether, police said. In the biggest such attack in western Europe since the London transport bombings in 2005, seven died when the bomb exploded on the Norwegian capital in mid-afternoon scattering glass, shattered masonry and twisted steel across the streets. Shortly afterward, a gunman opened fire at the youth camp of the ruling political party on Utoeya island, north-west of Oslo. Police said nine or 10 people were killed and they believed the two attacks were linked. The gunman was arrested. The bomb, which shook the city center at around 3:30 P.M. (1330 GMT), blew out the windows of the Prime Minister's building and damaged the finance and oil ministries. “People ran in panic,” said bystander Kjersti Vedun. The gunman, described by a police official as tall and blond, was reported by Norwegian media to have taken advantage of the confusion caused by the bombing to attack the summer camp of Stoltenberg's Labour party youth section. “There was a lot of shooting ... We hid under a bed. It was very terrifying,” a young woman at the camp told British Sky television. Deputy Oslo police chief Sveining Sponheim told reporters that the gunman in the Utoeya shootings had been disguised in a blue police-style uniform but had never been employed by the police. Acting Police Chief Sveinung Sponheim says a man was arrested in the shooting, and the suspect had been observed in Oslo before the explosion there. Sponheim said police were still trying to get an overview of the camp shooting and could not say whether there was more than one shooter. The United States, European Union, NATO and the UK, all quickly condemned the bombing, which Britain's Foreign Secretary William Hague called “horrific” and NATO Secretary-General Anders Fogh Rasmussen deemed a “heinous act.” In Washington, State Department spokeswoman Heide Bronke Fulton called the violence “despicable.” There has been no confirmation of any US casualties, she said. The US Embassy in Norway warned Americans to avoid downtown Oslo.