South Korean fighter planes were scrambled late last month as North Korean fighter jets flew dangerously close to the heavily-armed inter-Korean border, the Seoul-based newspaper reported Monday, citing a government source. "Four or five North Korean MiG jets crossed over the 'tactical action line' as far south as Kaesong City, prompting us to mobilize KF-16 fighters," the Chosun Ilbo daily quoted the source as saying. The North Korean jets turned back shortly afterwards, the source added. The incident came just after the North on October 19 threatened to attack Imjingak pavilion overlooking the border if Seoul allowed activists to send propaganda leaflets to the North. The tactical action line is a virtual line that the South Korean military has designated 20 to 50 km north of the demilitarized zone and the Northern Limit Line, the de facto maritime border, to respond to a North Korean provocation. The military will scramble fighter jets if North Korean planes cross over the line. South Korean Military officials said there is a strong chance that Pyongyang ordered the threatening maneuvers to show South Korea it was serious about attacking Imjingak as activists prepared to float 200,000 anti-communist leaflets to the North attached to helium balloons, according to the daily. Police in the event prevented the activists from launching their balloons from the pavilion. The two Koreas are still technically at war as the 1950-53 Korean War ended in a truce, not a peace treaty