South Korean government said it will intervene to stop a campaign, which plans to drop the DVDs of Hollywood film "The Interview" and other propaganda leaflets by means of balloons on North Korean territory. The statement, which cited a “limit” to freedom of expression, came as North Korea condemned the move and threatened retaliation. 

"If such a movement is detected in advance, the government will take necessary measures because it may threaten the security of residents there," Lim Byeong-Cheol, a spokesman for the South Korean unification ministry, said, Agence France-Presse (AFP) reported Friday.

Activists in South Korea reportedly plan to send about 10,000 DVDs of the movie and about 500,000 propaganda leaflets into North Korea. Park Sang-hak, head of Fighters for a Free North Korea, had said earlier this week, according to Yonhap, that the group was planning to scatter propaganda leaflets into the North on March 26, marking the sinking of a South Korean ship in 2010. He had said that the group will continue with the plan even if Seoul makes a formal request to halt the activity. In January, the group had claimed that it secretly sent about 100,000 leaflets into the North.

On Monday, the North responded to the planned campaign, saying that it was a declaration of war. "The act of leaflet scattering, which will be carried out amidst the rehearsal of war on North Korea, is an explicit declaration of war. ... “[We] do not hide the fact that we will counteract this time with cannons or missiles,” North Korea’s main propaganda website Uriminzokkiri said, according to Yonhap. 

A similar campaign had taken place last October, when balloons with about 200,000 propaganda leaflets were dropped into the North, which shot down a few of them. The incident had led to a series of gunshots from both sides.

"The Interview" is based on a fictional plot to assassinate North Korean leader Kim Jong Un. Last year, computer networks of Sony Pictures Entertainment were hacked and the attackers had demanded that the movie's release be halted. The hacking had soured North Korea's relations with the U.S. and South Korea.