Officials in the US and South Korea were scrambling yesterday to combat an unusually powerful cyber-attack that overwhelmed government and private sector websites in the two countries.

Many of the computers used to overwhelm targeted web pages in both countries were in South Korea, and authorities there said they suspected North Korea as being behind the electronic campaign. Tensions be-tween Pyongyang on one side and Seoul and Washington on the other have climbed recently following North Korean missile launches, a nuclear test and repeated threats of war.