North Korea's major websites suffered disruptions Sunday for the sixth straight day following Washington's warning of a "proportional" action against Pyongyang's alleged cyber attack on Sony Pictures Entertainment.
   
The homepage of the North's main propaganda organ Uriminzokkiri and two other sites whose servers are based in China were inaccessible Sunday morning.
  
North Korea's official portal site Naenara, whose server is based in Berlin, can be accessed only intermittently. But the websites of the North's official Korean Central News Agency (KCNA) and the communist party's official newspaper, the Rodong Sinmun, have been completely restored.
  
North Korea had experienced Internet outages for hours before coming back online Tuesday following a cyber security row with the U.S.
   
The U.S. blamed North Korea for hacking Sony Pictures to stop the Christmas Day release of "The Interview," a lowbrow comedy movie involving a fictional plot to assassinate North Korean leader Kim Jong-un. U.S. President Barack Obama had earlier pledged a "proportional" response to Pyongyang's recent cyber-attack.
   
North Korea has vehemently denied its involvement in the cyber-attack on Sony Pictures and offered to jointly conduct an investigation into the case with the U.S. government. (Yonhap)