China stressed it is opposed to all forms of cyberattacks but found no sufficient evidence to prove the United States' claim that longtime ally North Korea hacked into Sony Pictures.

The announcement did not mention a call from the United States to band together in fending off similar online attacks. Instead, China's foreign ministry spokeswoman Hua Chunying said there has to be a full evaluation of the facts before conclusions can be made.

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North Korea denied carrying out the hacking and warned the U.S. it will hit back for any retaliation. A group that took responsibility for the hacking said a Sony satirical film about the assassination of North Korea's Kim Jong-un angered its followers.

U.S. President Barack Obama earlier announced his administration will take measures against North Korea after the Federal Bureau of Investigation traced the Sony hacking to Pyongyang. It was the first time the U.S. openly accused another country of orchestrating such a cyberattack.

North Korea's top ally, China, is key to any U.S. measure to bear down on the north. But the U.S. is also wary of China and a U.S. official claimed the attack on Sony could have been sent through Chinese servers to mask its source.

Meanwhile, South Korea said computer networks at its nuclear plant had been hacked and non-critical data stolen, but ruled out dangers to nuclear facilities or reactors.

The announcement did not mention North Korea and officials could not authenticate Twitter messages claiming responsibility for the attacks and seeking the closure of three old nuclear reactors by Thursday.

TagsNorth Korea, Sony Pictures, hacking, Cyberattack