Several people were killed in Friday's massive bomb blast in central Oslo outside government offices and media buildings, Norweigan police said according to dpa. Police urged people to stay away from the centre of the capital and to refrain from using mobile phones to avoid overloading networks. Thor Langli, in charge of the police operation at the scene, told reporters he had no details of the exact number of fatalities but said 10 injured people had been taken to Oslo University Hospital. The blast damaged the facade of the government offices, including blowing out windows and the front of the 17-storey building that houses the prime minister's offices. Nearby ministries were also hit. "This is a very serious situation," Prime Minister Jens Stoltenberg, who was unharmed, told public broadcaster NRK. The premier declined to comment on possible motives, underlining the need for police and rescue services carry out their duties and at present the focus was on helping injured people.