PYONGYANG, Dec. 28-- Internet and 3G mobile network of the Democratic People's Republic of Korea (DPRK) were paralyzed again Saturday evening amid bickering between the United States and the Asian country over an earlier cyber attack on Sony Pictures.

At Pyongyang time 7:30 p.m. (1030 GMT) Saturday, DPRK's Internet and 3G mobile network came to a standstill, and had not returned to normal at press time as of 9:30 p.m.(1230 GMT) Saturday, according to Xinhua reporters and Chinese facilities based in the country.

Earlier in the day, the Policy Department of the National Defense Commission blamed the United States for enduring instability in the country's Internet and denied any cyber attack on Sony Pictures.

The United States groundlessly linked the unheard-of hacking at the Sony Pictures Entertainment to the DPRK, a spokesman for the department said in a statement.

The spokesman urged the United States to conduct a joint investigation with the DPRK.

The United States accused the DPRK of attacking Sony Pictures in late November to deter it from showing a comedy movie entitled "Interview" which features an assassination attempt on DPRK leader Kim Jong Un.

DPRK's Internet has been unstable since last weekend, including a complete outage of about nine hours on Tuesday.