Electronic jamming signals from North Korea have been affecting scores of civilian flights in and out of South Korea but did not endanger the aircraft, a Seoul official said Wednesday.
"We've confirmed the GPS (global positioning system) jamming signals have been stemming from the North," Lee Kyung-Woo, a deputy director at the state Korea Communications Commission, told AFP.
The transport ministry, in a statement and in comments to AFP, confirmed the jamming but did not say who was responsible.
The North has been accused before by Seoul of jamming GPS systems but there was no previous widespread effect on civilian flights.
A ministry statement said 241 flights by nine South Korean airlines and 11 flights operated by nine foreign airlines had been affected since last Saturday.
It said Seoul that day issued a warning notice for pilots and airlines.
Kim Choon-Oh, a ministry director, said GPS disruption was noticeable around Incheon airport, the South's main international airport.
"Authorities are tracing the origin," he told AFP.
"Despite disruption in GPS, there is no serious threat to the safety of flights because planes are using other navigation devices."
Kim said there was a brief disruption to the GPS systems of civilian flights last year, "but this kind of widespread disruption is unusual".
North Korea in recent weeks has frequently threatened offensive action including "sacred war" against the South.
It accuses its leaders of disrespect during Pyongyang's celebrations last month of the centenary of the birth of founding leader Kim Il-Sung.
A spokesman for Seoul's Joint Chiefs of Staff declined to say whether the jamming was also directed against the military. "There has been no problem in our military operations," he said.
The South's then-defence minister said in October 2010 that a North Korean jamming device capable of disrupting guided weapons posed a fresh threat to security.
Minister Kim Tae-Young told parliament the North had imported Russian equipment to jam South Korea's GPS reception and was capable of jamming reception over a distance of up to 100 kilometres (60 miles).
Kim said the North was thought to have been responsible for the intermittent failure of GPS receivers on naval and civilian craft along the west coast from August 23 to 25 that year.
In March last year the South's Yonhap news agency said the North had used jamming equipment to block South Korean military communication devices.
It said the strong jamming signals had caused minor disruptions to phones and navigational devices using GPS at military units near Seoul.