North Korea on Friday denied it had jammed the GPS systems of hundreds of civilian aircraft and ships in South Korea, accusing the South of using problems with navigation equipment to smear the North.

Pyongyang's telecommunications ministry spokesman said the South's allegations that the North jammed GPS signals from April 28 to May 13 were "sheer fabrication" aimed at slandering the communist state.

"The traitors' group was at first stupefied in the face of this chaos and then tried to slander us with fabricated allegations," the spokesman was quoted as saying by Pyongyang's official Korean Central News Agency.

The South was again displaying its "habitual bad behaviour of seeking to blame others for their own fault", he said.

"Repeating their bad habit of blaming others for their own problems, the traitors' group again revealed its true nature as a swarm of rats wearing human-shaped masks," he said.

South Korean officials said the signals, originating from the North's border city of Kaesong, forced sea and air traffic to use other navigational equipment to avoid compromising safety.

The GPS jamming incident came at a time of high cross-border tensions.

The North has threatened "sacred war" against the South in retaliation for perceived insults during Pyongyang's commemoration in April of the centenary of the birth of founding leader Kim Il-Sung.

The North has twice before been accused by Seoul of jamming GPS systems although there was no previous widespread effect on civilian flights.

South Korea complained about the jamming to Pyongyang, the International Telecommunication Union and International Civil Aviation Organisation.