OSLO - The US embassy in Oslo was hit by a loud explosion early on Sunday, causing minor damage but no injuries in what may have been a deliberate attack linked to the crisis in the Middle East, Norwegian police said.

"It's natural to see this in the context of the current security situation and that this could be an attack deliberately targeting the US embassy," Frode Larsen, head of the Oslo police investigation unit told a news conference.

No suspects have been identified at present but police are searching for one or several perpetrators and are cooperating closely with the embassy, Larsen said.

"One of our hypothesis is that this is terrorism, but we are also exploring other options," Larsen later told public broadcaster NRK.

The blast at the embassy compound in western Oslo occurred at 1 am (00:00 GMT), sending thick smoke into the street by the entrance of the consular section, eyewitnesses said.

Norway's government was in contact with officials at the US embassy to convey that this was "an unacceptable act that we take very seriously", Foreign Minister Espen Barth Eide, said in a statement.

"The security of diplomatic missions is very important to us," he said.

SMOKE AND DAMAGE

The blast occurred at the entry to the consular section, Oslo police said, and witnesses said the entrance had been damaged.

"There was a very thick layer of smoke on the street," said Sebastian Toerstad, 18, a high school student who drove past the embassy at the time of the explosion.

"There was some damage to the entrance," Toerstad told Reuters.

Police said no further explosive devices had been found in the area.

The US embassy referred all inquiries to the US State Department, when contacted by Reuters. The State Department did not immediately respond to a request for comment.

Reuters