A large explosion in Oslo shook Norway's government headquarters Friday afternoon. Hundreds of windows were shattered in the 17-story building that houses the Prime Minister's office, and up do a dozen people have been injured.

While the cause of the blast is currently unknown, some in Norway are speculating that it was a terrorist attack.

Norway seems like an unlikely target for militant extremism, but the theory cannot be ruled out. Norway was involved with the Muhammad cartoon controversy of 2006, when a Danish cartoonist made questionable comic-illustrations of the Prophet Muhammad. Norwegian newspapers reprinted the cartoons, and the embassy in Syria was burnt by angry protestors. However, much of the militant ire has been focused on Denmark.

Another report suggests that militants attacked Norway for its involvement in the war in Afghanistan, although the country is only the 18th largest international force in Afghanistan, with about 500 troops and personnel.

Perhaps the most logical reason that Norway would be attacked by terrorists concerns Iraqi-born cleric Mullah Krekar. Krekar is the founder of the Kurdish Islamist group Ansar al-Islam, and had been living safely in Norway since the 1990s. After a number of arrests and releases, a judge on July 12 filed terror charges against Krekar, who has been scheduled to be deported to Iraq since 2005.

Al-Qaeda also considers Norway part of the Jewish-Crusader alliance.

What is known, is that three Muslim immigrants were arrested in Norway and Germany earlier this month for planning a terrorist attack involving peroxide bombs.

IBTimes will be updating the story as it develops.