PAJU, South Korea, Dec. 2 -- Park Sang Hak, a North Korean defector, launches balloons bound for his homeland. They carry leaflets accusing North Korean leader Kim Jong Il of being a drinker of pricey wine, a seducer of other men's wives, a murderer, a slaveholder, a dictator and "the devil."

The South Korean government says it wishes Park wouldn't rain all this provocation on a heavily armed neighbor, but it says it is powerless to stop him. So about the only thing that usually stops Park's balloons is a wind that won't blow north.

But on Tuesday morning here at Paju, near the demilitarized zone that separates the two Koreas, Park and his compatriots ran into a bunch of South Korean activists willing to fight to keep the balloons on the ground. Park's anti-Kim leaflets, they shouted, were a threat to peace on the Korean Peninsula.

A balloon-driven rumble broke out. Scores of police struggled to keep it from turning into a full-blown riot. Before it was over, Park kicked one of the counter-protesters squarely in the head -- a blow that sounded like a bat whacking a hardball. He spat on several others who were trying to rip apart bags of leaflets. He pulled a tear-gas revolver from his jacket, and fired it into the air before police grabbed it.

In the end, Park's group managed to launch just one of its 10 balloons. Thousands of leaflets were torn from bags and spilled onto the ground.

Ballooning in the Korean borderlands, it seems, has become a contact sport.

Leaflets dropped this fall in the North have infuriated the government there, which is believed to have become particularly sensitive to personal attacks aimed at Kim since the stroke he reportedly suffered in August and the subsequent firestorm of speculation about his mental and physical competence.

The leaflets have been an aggravating factor in the North's unusually belligerent behavior this fall toward the government of South Korea. Effective this week, the North drastically cut access for South Koreans working at the Kaesong industrial complex, located just north of the border.

The restrictions slash the number of South Koreans permitted to stay in the factory complex, from 4,200 to 880. The North has also suspended cross-border train service and halted nearly all tourist access across the border.

Leaflets falling from the sky have added fuel to a fire that began to burn when South Korean President Lee Myung-bak took office in February and pledged to reverse a 10-year-old policy of giving substantial and largely unconditional aid to the North.

Lee halted the South's annual massive shipment of free fertilizer to the impoverished North, which suffers from chronic food shortages. He has also declined to move ahead on cross-border economic projects -- which had been negotiated with Kim by Lee's predecessors -- until the North makes progress on nuclear disarmament and human rights.

North Korea, in reaction, claims that the South is engaged in a "racket of confrontation" that goes "beyond the danger level, despite repeated warnings."

As the balloon imbroglio made clear here Tuesday, not all the anger is in North Korea.

Supporters of the two South Korean presidents who preceded Lee -- Kim Dae-jung and Roh Moo-hyun -- have voiced worry that a decade of political and economic cooperation between the two Koreas is being jeopardized.

Protesters here chanted that Lee's government should stop the balloons, honor the South's previous commitments to invest in the North and save the Kaesong complex, where 88 South Korean companies have invested more than $440 million to build factories that employ 35,000 North Koreans.

In Seoul, several North Korea experts say Lee will probably have to find a face-saving way to calm North Korean nerves or risk an escalation in political tension that could further damage investor confidence in South Korea's crisis-weakened economy.

"Lee's government will make a critical mistake if it conditions all aid on change in North Korea," said Koh Yu-hwan, a professor of political science at Dongguk University in Seoul. "Kim Jong Il's government will not change until it collapses."

One person with no interest in calming tension between the two Koreas is Park, the North Korean defector and activist.

"Hatred of Kim Jong Il motivates me," he said.

Park, 39, defected with his mother and two brothers in 1999, leaving behind his fiancee and two uncles.

"My uncles were beaten to death in prison," he said. "North Korean intelligence people visited the woman I was engaged to. They sexually abused her. I regret leaving her behind so much."

Thanks to his father's high position in the government, Park said, he had lived a relatively comfortable, even elite, life in Pyongyang, the North Korean capital. He was a member of the propaganda department of the Kim Il Sung Socialist Youth League, a group named after North Korea's founder, who is also the father of Kim Jong Il.

But Park and his family fled, he said, when his father -- then a Japan-based spy for the North Korean government -- warned them that the family might soon be caught up in a purge of intelligence officials.

With the help of his father's contacts in the security forces, Park and his family found their way to the Chinese border, swam across a river and eventually reached South Korea, he said.

Park is now chairman of Fighters for Free North Korea, a group based in Seoul. His work has won him international recognition. In September, he joined dissidents from around the world at a luncheon hosted by President Bush in New York.

Balloons became part of Park's life when he learned that the South Korean Defense Ministry had used them to deliver propaganda to the North, a practice that ended after a conciliatory North-South summit in 2000.

The long, tube-shaped balloons that Park launches are made by hand from sheets of vinyl and filled with hydrogen at the border. Helium is too expensive, Park said.

He said he has sent nearly 2 million anti-Kim leaflets north by balloon. Since April, he added, each of the waterproof leaflets has been attached to a U.S. dollar bill. Funding comes from individuals in South Korea and the United States, he said.

Park said he has asked the U.S. State Department for money, but it has not given him any. "Because of my balloons, the North Koreans are rounding up anyone with one dollar," Park joked Tuesday morning -- before he had to fight to launch his balloons.

It took more than an hour of pushing and shoving, and the help of a phalanx of South Korean policemen, before Park and others could launch a single balloon.

After it had soared into a cloudless sky and was carried north by the breeze, Park taunted his adversaries.

"You are the running dogs of Kim Jong Il!" he shouted. "You are trash!"

"You are afraid of unification!" they shouted back.

Park replied, "I am going to launch balloons every day, if the weather permits."