An explosion has damaged government buildings in Oslo with injuries reported. The cause of the blast has yet to be ascertained. If you have any information please email me at haroon.siddique@guardian.co.uk or contact me via Twitter @haroon_siddique 4.39pm: According to reports from the newspaper Dagsbladet, the bomb was meant to target the office of the oil and energy ministry, Lars Eriksen in Demark informs me. Rumours have been rife of additional bombs (possibly two more) in Oslo. NRK (the state broadcaster) is saying police believe there are no more bombs. But Nicholas Karlsen in Oslo emailed me to say that Aftenposten newspaper is reporting police believe it is possible there two more bombs that they haven’t located yet. 4.25pm: Peter Beaumont, foreign affairs editor at the Observer, says a jihadist group is most likely to be behind the blast: It has been known for some time that al-Qaida core and other related “franchises” – including in the most active in Yemen – have been attempting to develop operations. Which leads to a second question: why Norway?… The answer to that is three fold. In then first instance, with the increased levels of security and surveillance in the UK and the US as well as other European capitals, Norway might have been seen as a softer target despite the recent breaking up of an al-Qaida cell in Norway. A more detailed explanation of the problems that Norway has had with Al Qaeda were supplied a year ago by the Atlantic magazine i n an article by Thomas Hegghammer , a senior fellow at the Norwegian Defence Research Establishment in Oslo, and Dominic Tierney. That piece followed the arrest of three men in Norway and Germany for allegedly plotting a terrorist attack involving peroxide explosives. All of those arrested were were Muslim immigrants to Norway. The first explanation,” wrote Hegghammer and Tierney, “is Afghanistan. Norway has been part of the International Security Assistance Force (ISAF) in Afghanistan from its foundation in late 2001…. In late 2007, for example, Ayman al-Zawahiri, al-Qaida’s second-in-command, said that the group had previously threatened Norway because it “participated in the war against the Muslims… A second contributory factor for why Norway may have been eyed in the past for potential jihadi terrorist attack is the fact that in 2006, a Norwegian newspaper reprinted a series of Danish cartoons depicting the Prophet Muhammad which prompted threats against the country. A third potential explanation is the recent decision last week by a Norwegian prosecutor filed terror charges against an Iraqi-born cleric for threatening Norwegian politicians with death if he’s deported from the Nordic country. The indictment centered on statements that Mullah Krekar – the founder of the Kurdish Islamist group Ansar al-Islam – made to various media, including American network NBC. 4.14pm: The Norwegian state broadcaster now says two people are confirmed dead . 4.11pm: Oslo police also referred to “deaths and injuries” but did not specify numbers. So far one person has been confirmed dead as a result of the explosion, which police now say was caused by a bomb. 4.09pm: Oslo police have said the explosion was caused by a bomb, the BBC just said. 4.05pm: ABC News reports that the “was [the] result of a massive vehicle bomb, according to US government sources on the scene”. Swedish reporter Carl Kleberg has tweeted this: Police stops reporter of #Norway’s Aftenposten: “because there are still two bombs that we don’t know where they are.” #Oslo 3.59pm: An Icelandic MP has tweeted that seven people have been admitted to hospital in Oslo. Eyewitnesses say there are many ambulances on the scene. Mike Emery, working in Norway for a charity, emailed me: According to NRK (Norwegian public service broadcaster) there is broken glass up to 1km from the blast site. July is the holiday month in Norway and almost everyone goes on vacation. We have to hope that many people are on holiday. The blast happened after 3.15pm and Norway is on Summer Working Hours meaning people leave work at 3pm. Let’s hope this is the case. 3.51pm: Here’s another video showing the extent of the devastation wreaked by the explosion . _ 3.45pm: NRK, the Norwegian broadcaster, says that one person has been killed , Lars Eriksen in Denmark informs me. Senior adviser Oivind Ostang told Norwegian TV2. We can confirm that everybody who was working in the prime minister’s office today are safe. The only thing I know is that there has been a fire or something approaching a fire in the R4-buildling which houses the oil- and energy office. 3.42pm: This video shows windows blown out and people walking over pavements covered in shattered glass . 3.40pm: A Norwegian reporter told the BBC she is in a buidling five blocks away and its windows have been blown out by the explosion. She used the word “bomb” before clarifying that she had no evidence the cause of the explosion was a bomb but suggested that she could not see what else would cause an explosion of such magnitued. 3.34pm: Several people have been injured in a large explosion which has damaged government buildings in central Oslo, including the office of the Norwegian prime minster. A Reuters correspondent said he counted at least eight injured people after the unexplained blast. The tangled wreckage of a car was outside one building but the cause of the blast was unknown with police and fire officials refusing to comment. The explosion at around 3.30pm (2.30pm BST) blew out most windows on the 17-storey building housing prime minister Jens Stoltenberg’s office, as well as nearby ministries including the oil ministry, which was on fire. Norwegian news agency NTB said the prime minister is safe. Newspaper offices in the area were also reportedly damaged. The city centre – which usually empties in July as Norwegians take holidays – is currently closed off with all public transport to and from the centre suspended. Norway Haroon Siddique guardian.co.uk