SEOUL, South Korea — North Korean defectors vowed today to disrupt the South Korean leg of the Olympic torch relay in protest of China's repatriation of refugees to the North where they could face execution.

The demonstration would add to the chorus of protests that has dogged the torch's global tour, focusing attention on unrest in Tibetan areas of China and Beijing's human rights record.

Han Chang Kwon, head of a coalition of groups representing North Korean defectors in South Korea, told The Associated Press that the protest at the Seoul relay on Sunday could become violent. He did not elaborate.

The flame was set to arrive in Seoul early Sunday from Japan and head to Pyongyang, the North Korean capital, on Monday.

Han said the defectors in South Korea were "boiling with anger" because some who escaped to China from the North had been repatriated, adding that he hoped the protest would give North Korean leader Kim Jong Il "a stroke."

"While trying to improve its image with the Olympics, it (China) keeps sending defectors to the North knowing they will be executed or sent to political prisons," Han said.

A South Korean aid group, Good Friends, claimed last month that the North executed 15 people in February for attempting to flee or helping others escape the country, and the Amnesty International urged Pyongyang to halt such summary executions.

North Korea has never acknowledged the practice, claiming any allegations of human rights abuses in the country are groundless and part of a U.S. attempt to overthrow the regime.

Police officials have said they will arrest anyone who tries to interrupt the torch relay, which will follow a 15-mile route from the Olympic Park in southern Seoul to City Hall.

They also plan to dispatch some 8,000 riot police to guard the flame, while deploying some 100 officers with marathon-running experience to run next to the torch in shifts.

The U.S. Embassy has advised its citizens to stay away from the route to avoid possible clashes.

Thousands of North Koreans are believed to be hiding in China after fleeing their homeland. On Friday, U.S.-based rights group Human Rights Watch urged South Korea to pay more attention to their plight.

On Saturday, heavy security and a large contingent of pro-China supporters thwarted protesters who tried to disrupt the Japanese leg of the Olympic torch relay in Nagano.

Five men were arrested, in all. Three were apprehended after trying to charge the torch, the fourth threw eggs and the fifth hurled tomatoes at the flame.

The international route ends next week, when the flame arrives in Hong Kong on Wednesday. It will then travel throughout China ahead of the Aug. 8 start of the games.

The relay, the longest in Olympic history, has been a lightning rod for anti-China protests, largely in response to China's crackdown last month on anti-government riots in Tibet, which it has governed since the 1950s.

North Korea, which tolerates no dissent, has vowed to make its leg of the relay the most secure and smooth.

China is the North's only major ally and provides its impoverished neighbor with food and energy aid.

Associated Press writer Jim Armstrong contributed to this report from Nagano, Japan.