North Korea must compensate Sony for cyber attacks: US

"If they want to help here they could admit their culpability and compensate Sony for the damages that they caused," deputy State Department spokeswoman Marie Harf told reporters.

Washington accuses Pyongyang of being behind the hack that led to the release of embarrassing company emails and caused Sony executives to halt the debut of the comedy action film "The Interview."

The film about a fictional CIA plot to kill the country's leader infuriated North Korea, although Pyongyang has repeatedly denied it was behind the cyber assault.

Washington is "confident the North Korean government is responsible for this destructive attack," Harf insisted.

The government of the hermit state also has a "long history of denying responsibility" for provocative actions, she added.

Asked about threats from Pyongyang to hit back if it is sanctioned over the Sony affair, Harf said: "We do urge North Korea to exercise restraint, to refrain from further threatening actions at this time."

President Barack Obama, while saying the alleged hack was not an act of war, has promised an unspecified "proportionate" response.

Harf said she could not comment on online reports that alleged North Korea's limited Internet connectivity had been sharply curtailed Monday, suggesting it was under attack.

The US administration is "discussing a range of options" in response to the Sony hacking, she said, stressing however that Washington would not outline publicly what moves it planned to take.

"As we implement our responses, some will be seen, some may not be seen," she said.