Balloon-carried leaflets sent by South Korean civic groups to North Korea are unnerving the North Korean authorities as the anti-Pyongyang messages are gaining trust among North Korean citizens, a local daily said on Saturday.

In the past, when the anti-North Korean leaflets were spread in Pyongyang, North Korean residents didn't believe their contents. However, the situation is different now. According to the Chosun Ilbo, civic groups' leaflets these days are much more effective than in the past as they are now written by North Korean defectors who write contents that ring a bell among northerners.

The leaflets also contain the private life of its leader Kim Jong-il of whom North Koreans are very curious, it said.

When leaflets fell down on the streets of Pyongyang last summer, carried by dozens of balloons, revealing the corrupt life of Kim Jong-il and criticizing the North's repressive regime, the local security apparatus went into a state of alarm. They ordered citizens to stay in their houses. Only after all the leaflets were collected, they allowed people to come out from their residences.

North Korean authorities are responding angrily. In recent days, they repeatedly told the South Korean authorities to ban the sending of anti-North Korean leaflets by the civic groups in South Korea, including the specific names and organizations involved. They threatened that if situation is not taken care of by the South authorities, the North "will take the matter on its own hands," according to the report.

Park Sang-hak, a representative of the Coalition for Free North Korea Movement in Seoul, is undaunted. "Sending leaflets to North Korea is the least we can do for North Koreans to help them to know what is true. I will not yield to the threats."