See our slide show of early images from downtown Oslo after the blast here.
UPDATE NO. 48/11:10 p.m.: Police have IDed the gunman as Anders Behring Breivik, a Norwegian man they characterized as a right-wing domestic extremist with no ties to jihadi terror groups, the New York Times reports.
UPDATE NO. 47/10:26 p.m.: Norwegian police now say that at least 80 people were killed during the shooting spree at the youth camp on the island of Utoeya, the BBC reports.
"It goes without saying that this gives dimensions to this incident that are exceptional," a police spokesman said.
Officials had previously warned that they expected the death toll to rise overnight, but the new figure far exceeds even the most pessimistic reports from earlier in the day.
Police had previously confirmed nine or 10 people had been killed during shooting. An eye witness, meanwhile, had told media outlets that he had seen 20 dead bodies on the island.
UPDATE NO. 46/6:20 p.m.: It appears as though things are relatively under control in Norway. At last count, at least 16 people are dead (seven from the blast, and nine from the shooting.) Police say they expect the death toll to rise overnight.
We'll continue to update with any major developments, but for now this will probably bring our string of live updates to an end.
We'll leave you with a quote from Norway Prime Minister Jens Stoltenberg: "We're a small country but a very proud country. No one can bomb us to be quiet. No one can shoot us to be quiet no one can ever scare us from being Norway."
UPDATE NO. 45/5:42 p.m.: Oslo police say the suspect in custody is 32 and "ethnic Norwegian," according to the BBC.
UPDATE NO. 44/5:35 p.m.: Looks like as bad as things were, they could have been worse. Sky News reports that Norwegian police now say they found "undetonated explosives" on Utoya Island, the location of the youth camp.
UPDATE NO. 43/5:30 p.m.: The initial focus for much of the day was on a potential link to al-Qaida, but as the day progressed -- and more info surfaced about the gunman in custody -- the attention has increasingly shifted to domestic extremism.
BBC News security correspondent Gordon Corera reports: "The choice of targets - government buildings and a political youth rally - suggested a possible political agenda rather than the mass casualty approach typically employed by al-Qaida."
UPDATE NO. 42/5:12 p.m.: Prime minister says nation's top priority is to "comfort and care for people who have lived through a nightmare which very few of us can imagine." He's now done speaking and is on his way to visit some of the injured at the hospital.
Norwegian authorities are no longer keeping his location secret, so that suggests (we hope, anyway) that they believe they have the situation under control.
UPDATE NO. 41/5:06 p.m.: The prime minister says he will not confirm or deny any reports of groups taking responsibility for the attacks.
UPDATE NO. 40/4:54 p.m.: More of the prime minister's remarks (via the Telegraph):
"I have message to the person who attacked us and the people who are behind it: You're not going to destroy us. You're not destroying our democracy and our work for a better world. We're a small country but a very proud country. No one can bomb us to be quiet. No one can shoot us to be quiet no one can ever scare us from being Norway."
UPDATE NO. 39/4:49 p.m.: Norway's justice minister has confirmed that the suspect in custody is Norwegian, BBC reports.
UPDATE NO. 38/4:45 p.m.: Speaking a press conference, Norwegian Prime Minister Jens Stoltenberg said: "We will find the guilty and hold them responsible ... No one will bomb us to silence. No one will shoot us to silence. No one will ever scare us away from being Norway."
UPDATE NO. 37/4:34 p.m.: A little more info on the description of the gunman in custody: Police say he is tall with blonde hair, CNN reports. "Nordic appearance," police said.
UPDATE NO. 36/4:25 p.m. ET: Speaking with the BBC, Oslo's mayor said that authorities are not yet sure whether the attackers were the work of a lone man or that of a larger group. "It's crazy either way," he said.
UPDATE NO. 35/4:05 p.m. ET: Oslo police say that the gunman arrested at the youth meeting had previously been spotted in the capital prior to the explosions. That news has many hoping that the attacks were the work of a lone terrorist and not a coordinated attack.
Elsewhere, a foreign minister tells the BBC that the gunman in custody is Caucasian.
UPDATE NO. 34/4 p.m. ET: A terrorism expert tells the BBC that he believes that Ansar al-Jihad al-Alami (the Helpers of the Global Jihad), the jihadi terror group that has claimed responsibility for the blast, was not behind the attack.
UPDATE NO. 33/3:46 p.m. ET: Police now put the death count on the island at at least nine, BBC reports. (CLARIFICATION: BBC had originally reported the total was at least 10.)
UPDATE NO. 32/3:40 p.m. ET: Police have now confirmed that several people have been killed in the shooting at the youth camp, but say an exact number is unavailable, Reuters reports.
An eye witness previously told Reuters and the AP that he saw at least 20 dead on the island.
UPDATE NO. 31: "We will work with Norway to hunt the murderers who did this," British Prime Minister David Cameron said, BBC reports.
UPDATE NO. 30: The New York Times reports (via Norway media) that when the gunman arrived at the youth camp, he identified himself as a police officer “He said it was a routine check in connection with the terror attack in Oslo,” one witness told VG Nett, the website of a national newspaper.
UPDATE NO. 28: Police have confirmed that they believe the man arrested at the youth camp was connected to the Oslo bombing.
UPDATE NO. 27: A witness has told Reuters that he saw at least 20 dead at the youth camp. Police have declined to comment on the report.
UPDATE NO. 26: Plenty of footage of the aftermath is being posted to YouTube. You can scroll down a little to see some of the videos.
UPDATE NO. 25: The Norwegian prime minister has called an emergency crisis meeting of his government for later tonight, BBC reports.
UPDATE NO. 24: There are some unconfirmed reports by local media and on Twitter that the man who police arrested at the youth camp meeting had blond hair and blue eyes. Those reports have some speculating that the attack may have been the work of a domestic group.
Regardless, it appears way too early to draw any definitive conclusions.
UPDATE NO. 23: The Norwegian prime minister has given a number of phone interviews, but his location is being kept secret.
UPDATE NO. 22: The New York Times is reporting that the terror group Ansar al-Jihad al-Alami (the Helpers of the Global Jihad) is claiming responsibility for the bombing.
"What you see is only the beginning, and there is more to come," the group said in a statement, according to a translation provided to the paper by an independent terror analyst.
The claim has not be confirmed, and Norwegian officials have yet to publicly address the report.
UPDATE NO. 21: Oslo police say they can NOT confirm television reports of casualties at the youth camp meeting.
UPDATE NO. 20: Police now say they believe the Oslo blast and the youth camp shooting are related.
UPDATE NO. 19: Reuters is reporting that Norwegian police now fear that there may be explosives somewhere at the site of the youth camp meeting.
UPDATE NO. 18: Oslo police now put confirmed dead at seven from blast.
UPDATE NO. 17: In a sign that the shooting spree at the youth camp on Utoya is still not yet under control, authorities are advising Norwegians not to call people they know who may be on the island for fear "giving off the location of those who are hiding in the bushes and elsewhere on the island, to the shooter," BBC reports.
A clarification, the youth camp was for anyone under the age of 25.
UPDATE NO. 16: Still no word on who is responsible for the blast and/or the youth camp shooting. However, given both attacks appeared to target the ruling Labour Party -- and were not necessarily executed in an attempt to maximize civilian casualties -- many observers believe the two are connected.
UPDATE NO. 15: State TV now puts the death toll from the camp shooting at five.
UPDATE NO. 14: Police have arrested one person at the Labour Party youth camp, state TV reports.
UPDATE NO. 13: Washington Post has a list of Twitter accounts to follow for updates on the ground. Here it is.
UPDATE NO. 12: Sky News is reporting that at least four people have been killed at the youth meeting.
Latest reports say that the prime minister was not set to appear at that meeting until tomorrow. Authorities have sent an anti-terror unit to the scene and are evacuating the area.
UPDATE NO. 11: Reuters is reporting that at least 11 people have been admitted to the Oslo hospital, many of which are seriously injured.
UPDATE NO. 10: Police now say that there are "a lot" of casualties from the blast.
It will probably be a while before we know the official number, as efforts currently appear focused on evacuating the area and ensuring that there are no other bombs in the area.
Meanwhile, reports on the ground say that at least five people have been injured at the youth camp, where a suspect dressed as a police officer opened fire shortly after the blast.
UPDATE NO. 9: UN Secretary-General Ban Ki-moon is expected to make a statement regarding the attack shortly.
UPDATE NO. 8: Still too early to know for sure if the youth meeting shooting was part of a coordinated attack, but this sure makes it appear that way.
A Norwegian newspaper is reporting that the prime minister had been scheduled to appear at the meeting, which is on a small island south of Oslo.
UPDATE NO. 7: More scary news. Local police say that shots have been fired at a Labour Party youth meeting near Oslo after the blast in the capital.
The gunman was reportedly dressed as a police officer. No word on casualties.
UPDATE NO. 6: Police are now urging people to leave central Oslo, the BBC reports.
Latest reports have two confirmed dead and 15 injured.
UPDATE NO. 5: BBC reports that Norwegian police believe the bomb was the work of a terrorist group, although there is still no word on which one.
Reuters, meanwhile, has a breakdown of the possible groups it could have been. The leading suspect appears to be al-Qaida.
UPDATE NO. 4: The blast was caused by a massive car bomb, a U.S. government source on the ground tells ABC News.
ABC also reports that there was a second, smaller blast somewhere in the city.
UPDATE NO. 3: A Norwegian government minister tells the BBC that an unknown number of people are still trapped in the buildings near where the bomb went off.
The one small bit of fortunate news is that the blast occurred on a summer Friday afternoon, likely/hopefully meaning that fewer people were at their desks at the time of the blast than would have been normally.
UPDATE NO. 2: Several local news outlets are reporting that police believe that there may have been 2 other bombs around Oslo that did not explode, according to a Breaking News alert.
UPDATE: The death toll is now at two, according to state broadcaster NRK.
ORIGINAL POST: A loud explosion shook central Oslo on Friday, blowing out the windows of several government building including the one housing the Norwegian prime minister's office.
There were initial reports of multiple injuries and at least one person has been confirmed dead. According to local TV, the prime minister, Jens Stoltenberg, was not in his office at the time of the blast.
The exact details surrounding the explosion are still unclear, but police quickly confirmed that the blast was the result of a bomb.
Witnesses at the scene reported seeing the wreckage of a car near the blast site, leading to speculation that blast was a car bomb.
There have not yet been any terrorist groups stepping forward to claim responsibility for the blast.