It has emerged that North Korean fighter jets reportedly flew close to the Korean border late last month reflecting that tensions still hang in the air.

According to a Seoul report, the incident came after Pyongyang threatened to launch an attack if activists from the South float propaganda balloons across the border.

“Four or five North Korean MiG jets crossed over the Tactical Action Line as far as south as the North Korean border city of Kaeson, prompting us to mobilize KF-16 fighter jets,” Chosun Ilbo daily quoted a government source as saying, adding that the North Korean jets turned around shortly afterward.

Military officials believe that the maneuver was an act of provocation from North Korea. Defense Ministry spokesman Kim Min Seok declined to confirm the report, claiming he cannot comment on military intelligence matters. “We are closely monitoring every move on the North Korean side,” Mr. Kim said.

Pyongyang threatened a direct strike if activists send propaganda leaflets across the border. South Korea attempted to block the protest but the order was ignored by the activists.

Seoul’s defense ministry observed that North Korean military have been repositioned near the border and said South Korean forces are vigilant in case of an attack.