Seoul (AFP) - The United States has dismissed a call by North Korea for a joint investigation into the hacking of Sony Pictures and wants China to help block cyber attacks from Pyongyang.
Washington blames North Korea for a breach of cyber security at Sony which led to the release of embarrassing emails and prompted executives to halt the release of "The Interview".
The movie, which was due to open on Christmas Day, is a madcap romp about a CIA plot to kill leader Kim Jong-Un that has infuriated the secretive state.
Pyongyang has repeatedly denied that it was behind last month's crippling attack, which also led to the leaking of scripts, and called Saturday for a joint probe with the US.
But US National Security Council spokesman Mark Stroh said: "If the North Korean government wants to help, they can admit their culpability and compensate Sony for the damages this attack caused."
A senior US administration official told AFP that Washington had asked Beijing, Pyongyang's closest ally, to help block further cyber attacks.
The official said that during discussions on internet security both the US and China had "expressed the view that conducting destructive attacks in cyberspace is outside the norms of appropriate cyber behaviour".
Sony has defended its decision to cancel the release of "The Interview" after anonymous hackers invoked the 9/11 attacks in threatening cinemas screening the film. Theatres then said they would not show it.
The threat followed the November 24 hacking claimed by a group calling itself the Guardians of Peace (GOP), which led to the release of employee salaries data and health records.
The FBI blamed North Korea, saying attackers used malware to break into the studio and render thousands of Sony Pictures computers inoperable, forcing the company to take its entire network offline.
It said analysis of the software tools which were used revealed links to other malware known to have been developed by "North Korean actors".
The FBI also cited "significant overlap" between the attack and other "malicious cyber-activity" with direct links to Pyongyang, including an attack on South Korean banks carried out by the North.
On Friday President Barack Obama said: "We can confirm that North Korea engaged in this attack.
"We will respond. We will respond proportionately and we'll respond in a place and time and manner that we choose."
A foreign ministry spokesman in Pyongyang denied the accusation on Saturday.
- 'Hostile activities' -
"As the United States is spreading groundless allegations and slandering us, we propose a joint investigation with it into this incident," the spokesman was quoted as saying by the official Korean Central News Agency (KCNA).
The spokesman also threatened "grave consequences" if the US continued to discuss retaliation against North Korea on this matter.
"But in case we have to retaliate, we would not carry out terrorist attacks on innocent viewers at movie theatres but stage frontal attacks on those who are responsible for the hostile activities against the DPRK (North Korea) and their headquarters," he said.
Despite denying the attack, the North's top military body the National Defence Commission has slammed Sony for "abetting a terrorist act while hurting the dignity of the supreme leadership", according to KCNA.
Chinese state newspaper the Global Times has also criticised the movie, describing it as "senseless cultural arrogance" in an editorial.
Obama said there was "no evidence" that North Korea had acted in concert with another country after reports that China had possibly provided assistance.
The president also said that while he was sympathetic to Sony's plight, the movie giant had "made a mistake" in cancelling the release.
Free speech advocates and foreign policy hawks have slammed Sony's decision as cowardice in the face of a hidden enemy.
But Sony vigorously defended the move, saying it still hoped to release the film on a different platform -- perhaps on demand or even online for free.
"We have not caved, we have not given in, we have persevered and we have not backed down," studio boss Michael Lynton told CNN.