Updated

A North Korean defector tried to set himself on fire to halt the Olympic torch relay through Seoul, while thousands of police guarded the flame Sunday from protesters blasting China's treatment of North Korean refugees.

Hundreds of China supporters waving the Chinese flag greeted the torch, throwing rocks at anti-Beijing demonstrators. Police ran alongside the flame and rode horses and bicycles on the relay across the city, which hosted the 1988 Olympics.

The torch relay has become a lightning rod for anti-China demonstrations. At other stops, protesters have focused their ire on Beijing's recent crackdown on anti-government riots in Tibet. But in South Korea, China's treatment of North Korean defectors has taken center stage.

Thousands of North Koreans, fleeing lives of hardship in a country that restricts all civil liberties, have escaped across the loosely controlled Chinese border, rather than attempt the heavily fortified frontier with the South. Many live in hiding in China, where if caught, they are deported back home to face imprisonment in life-threatening conditions.

The man who tried to immolate himself, 45-year-old Son Jong Hoon, had led an unsuccessful public campaign to save his brother from execution in the North, where he was accused of spying after the two met secretly in China. About an hour into the relay, Son poured gasoline on himself and tried to light himself on fire, but police stopped him.

At the start of the relay, a protester rushed toward the Olympic flame and tried to unfurl a banner calling for China to respect the rights of North Korean refugees. Dozens of police surrounding the torch quickly whisked him away. As it approached the city center, another North Korean defector also tried to impede the run and was arrested.

Police said a total of five people were arrested. A police official near Olympic Park said one of the five was a Chinese student who was under investigation for allegedly throwing rocks. The official requested not to be named because an investigation was under way.

There were no further attempts to stop the torch on its 4 1/2-hour trip through Seoul to City Hall, where it was met by some 5,000 supporters.

Some 8,000 police were deployed across the South Korean capital to guard the torch on its 15-mile run from Olympic Park.

The first runner, the South's Korean Olympic Committee head Kim Jung-kil, jogged out of the park surrounded by police on horseback, on bicycles, in buses and on foot.

Thousands of Chinese also paced the torch. They carried a large red Chinese flag, chanting "Go China, go Olympics!"

Scuffles broke out near the park between a group of 500 Chinese supporters and about 50 demonstrators. The Chinese side threw stones and water bottles at the others as some 2,500 police tried to keep the two groups apart.

A rock hit a journalist in the head, but there were apparently no other injuries.

"The Olympics are not a political issue," said Sun Cheng, 22, a Chinese student studying the Korean language in Seoul. "I can't understand why the Korean activist groups are protesting human rights or other diplomatic issues."

Seoul is one of the last stops on the torch's international tour, which ends when the flame arrives in Hong Kong on Wednesday. On Sunday, three human rights activists who planned to protest the relay in Hong Kong were barred from entering the Chinese-ruled territory, local media and the one of the activists said.

The torch heads next to North Korea for its first-ever run in the communist country on Monday. Disruptions were not expected in the North, an authoritarian state that tolerates no dissent.