Washington, July 9 (DPA) The US believes North Korea was responsible for a massive cyber attack on government and other websites during the past week, Fox News reported Wednesday.

An unnamed US defence official told Fox the attack targeted dozens of websites, including the ones for the US Defence Department and the Department of State.

The attacks were also directed at South Korean websites, the Yonhap news agency reported. South Korean intelligence believes the attacks originated in North Korea, the report said.

The attacks involved ordering a huge number of computers to visit the websites simultaneously to overload the system and shut down ones not robust enough to sustain the traffic. US officials emphasised there was no security breach.

'It's just overloading the system,' the defence source told Fox.

US State Department spokesman Ian Kelly confirmed the department's website came under attack Sunday but the site was working fine.

'The attack is still ongoing, but it's much reduced,' Kelly said.