North Korean leader Kim Jong-il celebrates his 68th birthday on February 16.

One of the organizations involved is the Society for the Victims of Kidnapping, a group that campaigns for the return of South Koreans allegedly kidnapped by North Korean agents.

According to one of the group's leading members, each balloon will carry enough North Korean money to buy one kilogram (2.2 pounds) of rice.

"We are sending money to our family members, who are dying of starvation," Choi Sung-yong was quoted as saying during a press conference in Seoul.

However, a spokesman for the Minister of Affairs for the National Union of the Republic of Korea Kim Ho-nyeon told the South Korean news channel YTN that the activists had not received permission from the government to send monetary aid, and could face up to three years behind bars or a fine of just over $10,000 if they went through with their attempt.

"In order to send North Korean money over the border, permission needs to be attained and the Ministry of Affairs for the National Union of the Republic of Korea has not given such permission," Kim said.

Relations between Seoul and the communist North have deteriorated since South Korean President Lee Myung-bak took office in February 2008.

After coming to power last February, Lee said he would review agreements reached at the 2000 and 2007 inter-Korean summits, and demand more in return from the North for the economic support provided by Seoul.

North Korea said on Friday it would scrap all political and military agreements with South Korea, including a non-aggression pact, over its neighbor's "hostile intent."

The two countries are still technically at war as their 1950-53 conflict ended in a truce rather than a peace treaty.