Seoul, March 23 (IANS): Activists against the North Korean regime on Monday cancelled their plans to this week send balloons carrying propaganda against it from the South Korean border, following heated exchange of military threats between the two countries, Efe news agency reported.

“Fighters for Free North Korea”, a group of mostly North Korean refugees in South Korea, has decided to postpone the launch of balloons carrying pamphlets and DVDs, the group's leader Park Sang-hak told media.

The group had planned to launch 500,000 pamphlets carrying anti-regime propaganda and copies of “The Interview”, a comedy film ridiculing North Korean leader Kim Jong-un, on Thursday marking the fifth anniversary of North Korea sinking Seoul's naval vessel Cheonan.

The organisation's head told Yonhap news agency that it would go ahead with the launch later unless North Korea apologised for the incident.

On March 26, 2010, the Cheonan was attacked with torpedoes that left 48 people dead, for which Seoul blamed Pyongyang.

The balloon-launch plan has sparked high military tension between the two Koreas as the Kim Jong-un regime threatened to open fire on South Korean territory in case the balloons were launched.

The South Korean government, on its part, announced Monday that it would respond strongly to any such aggression by the North Korean army.

North Korea considers propaganda launches of this nature to be a serious offence and it has been the source of tension on earlier occasions.

The most serious incident took place in October last year when Pyongyang shot at the balloons, which led to an exchange of fire with South Korea, though without incidents.

This controversy coincides with a period of tension in the Korean peninsula due to the joint military drills conducted by Washington and Seoul in South Korean territory.

North Korea considers these drills to be a rehearsal for an invasion against it and has responded by issuing strong threats and launching missiles into the sea.