New Delhi, March 8 -- An overnight explosion at the US Embassy in Norway may have been a terrorist act, though authorities are also examining other possible causes, police in Oslo said on Sunday.

The blast occurred around 1:00 am (0000 GMT) at the entrance to the embassy's consular section. No injuries were reported, and the incident caused only minor material damage. Officials did not disclose details about the exact cause of the explosion but confirmed that an "explosive device" had been used.

Norway's Prime Minister Jonas Gahr Store called the incident "very serious and completely unacceptable". In a statement, he said he had spoken with the head of the US embassy in Oslo on Sunday.

PM Store said security had also been beefed up at ...