Norwegian authorities have detained three brothers believed to be responsible for the bombing at the U.S. embassy in Oslo on Sunday, an act they’ve labeled as terrorism.

The explosion, thought to be from an improvised explosive device (IED), caused significant damage to the embassy’s entrance but left no casualties, according to officials. The suspects, Norwegian citizens with Iraqi roots, have yet to be questioned, police report.

The investigation continues to explore whether the attack was connected to turmoil in the Middle East, with possibilities of foreign state involvement being considered. This incident aligns with heightened alerts in Europe due to ongoing conflicts involving the U.S. and Israel.

(With inputs from agencies.)