"Two slow-flying aircraft presumed to be MI-2 choppers were spotted flying from skies near Kaesong close to the TAL yesterday morning," a military source here said Sunday.

South Korean fighter jets were scrambled on Saturday morning as two slow-flying North Korean helicopters flew south close to the tactical action line set by South Korea.

The TAL was set by the South Korean military 20 to 30 km north of the military demarcation line and the Northern Limit Line, the de facto maritime border. It was drawn up because it would be too late for the South Korean Air Force to respond if North Korean fighters come any closer to the border.

Fighter jets are automatically scrambled if any North Korean aircraft come near or cross the TAL.

In the past when tensions were high across the border, North Korean fighters crossed the TAL scores of times a year, but almost nothing of the kind had happened this year.

But a military spokesman said North Korea did not violate a no-fly zone set last month under an inter-Korean military agreement of September, which stretches 10 km on both sides of the military demarcation line.

Military authorities reportedly believed that the North Korean choppers were carrying personnel and landed at a base near Kaesong.