Police block vehicles carrying anti-North Korea civic activists on a road leading to the Imjin Pavilion Monday. (Ahn Hoon/The Korea Herald)

The military and police blocked civic activists from sending propaganda leaflets over to North Korea on Monday but military tension remained high across the border as they vowed to go ahead with their plans.

The Army said it would maintain vigilance for the time being ready to exercise self-defense measures should it see signs of imminent attack from the communist state.

A group of South Korean conservatives and defectors were blocked by the police on Monday from entering Imjin Paviliion in Paju, Gyeonggi Province where they planned to release balloons carrying leaflets criticizing the Kim Jong-un regime.

South Korea has put its frontline units on high alert against possible attack from the communist state. 

North Korea threatened last week to strike South Korea’s western areas should South Koreans, including defectors, send leaflets over to its side. The announcement came after the group said they planned do so of Imjin Pavilion on Monday.

The Gyeonggi Provincial Police Agency dispatched police, in collaboration with the military, to Imjin Pavilion on Monday to block the group from entering the area, according to the Defense Ministry.

The ministry said that it had tightened its military readiness whether or not leaflet balloons would be flying to the North.

Defense sources told local media that South Korea was ready to scramble fighter jets, and has put its artilleries and rocket launchers in place for possible combat. The communist state has been reportedly preparing its artillery since it gave its warning to the South.

The Defense Ministry declined to disclose the weapon status intelligence of the two Koreas due to national security.

Last week, Defense Minister Kim Kwan-jin visited military units on the central front, ordering his troops to be on alert and ready to fire against possible provocations from North Korea.

South Korea’s Joint Chiefs of Staff Chairman Jung Seung-jo also visited a military base on Sunday and commanded his troops to keep their weapons and equipment ready and in best shape to immediately counter attacks from North Korea.

South Korea has been strengthening its defense and security measures on the border since the defection of a North Korean soldier, who crossed the demilitarized zone without being detected.

The incident cost several commanding officers their posts after President Lee Myung-bak reprimanded Minister Kim for failing to maintain tightened security at the border.

By Park Hyong-ki (hkp@heraldcorp.com)