The group of about 40 activists also burned images of Kim and a North Korean flag that were printed on large placards.

The black-and-white leaflets criticized Kim's harsh rule and urged North Koreans to rise up against his regime. They also said Kim had suffered a stroke recently.

South Korean and U.S. officials have said North Korea's 66-year-old leader may have suffered a stroke, but North Korea has denied it.

"Condemn Kim Jong Il," the group chanted as a balloon was released into the air - one of nine filled with propaganda and sent across the heavily militarized border.

Defectors and anti-Kim activists scuffled with protesters trying to stop the leaflet campaign near the border on Tuesday. Left-wing activists said the leaflets hurt inter-Korean relations, and they condemned the South Korean government for not cracking down on the propaganda effort.

The South Korean government ended decades of propaganda warfare under a 2004 deal with North Korea amid reconciliation on the peninsula.

But South Korea says it cannot ban its citizens from sending the flyers because they have a right to exercise freedom of speech. The government has, however, asked the activists to stop the practice.

The North officially complained about the leaflets in October and warned of grave consequences to joint cross-border projects unless the leaflet campaign ended.

North Korea began restricting traffic through its border with South Korea on Monday as a first punitive step against the South.

Relations between the two Koreas have deteriorated since South Korea's conservative President Lee Myung-bak took office in February with a pledge to take a firmer position on the communist North than his liberal predecessors.

The 40-foot-tall (12-meter-tall) balloons - fueled by hydrogen and shaped like missiles - are the most direct way for activists to reach people living in one of the world's most isolated nations.

The two Koreas have been separated by troops, tanks and one of the world's most heavily armed borders since a three-year war ended in a truce in 1953.