New Delhi, March 8 -- An explosion struck the United States embassy in Oslo in the early hours of Sunday, shattering the quiet of a residential neighbourhood, sending a bomb squad and police helicopters scrambling to the scene, and prompting an investigation that Norwegian authorities say is still in its earliest stages.

An apparent act of sabotage targeted the consular section of the American diplomatic compound in western Oslo at approximately 1 a.m. local time (0000 GMT), causing minor structural damage but no casualties. The blast, which was heard across surrounding streets and prompted dozens of calls to emergency services, has placed one of Europe's most stable capitals on an unexpected security footing.

"At around 1:00 am we rece...