The United States on Monday insisted on blaming the Democratic People's Republic of Korea ( DPRK) for a cyber attack on the U.S.-based Sony Pictures Entertainment, demanding Pyongyang compensate for the damages caused.

"Well, as the FBI and the president and everyone who's now made clear we are confident the North Korean government is responsible for this destruction attack. We stand by this conclusion," said Marie Harf, deputy spokesperson of the U.S. State Department, at a news briefing.

The U.S. Federal Bureau of Investigation (FBI) claimed Friday that it had "enough information" to conclude that the DPRK was responsible for hacking into Sony computers and posting online some of the stolen data in late November.

Sony (SNE, quote) last week canceled the planned Dec. 25 release of its comedy movie "The Interview," which depicts a fictional assassination attempt against the DPRK leader Kim Jong Un, after major U.S. cinema chains decided not to show the movie as the hackers warned movie-goers to stay away from cinemas screening the film.

While speaking at his end-of-the-year news conference Friday, U. S. President Barack Obama said Sony made a mistake by canceling the release of the movie. He also said he wished the company had contacted him directly before taking the action, vowing to " respond proportionally" to the cyber attack.

The DPRK on Saturday flatly rejected the U.S. accusations and proposed a joint investigation with the United States. In response, Harf said that, if Pyongyang wants to help, "they can admit their culpability and compensate Sony for the damages that they caused."

"We do urge North Korea to exercise restraint, to refrain from further threatening actions at this time. Obviously, we talked about this a lot in the last few days, but that's what we're focused on right now," Harf said.

Harf declined to tell in detail about what the U.S. retaliatory measures will be in response to the cyber attack, reiterating that the U.S. would implement its responses. "Some will be seen, some may not be seen," she said.

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