BEIJING (AP) — The Olympic flame approached the final destination of its long and sometimes contentious global tour Wednesday, greeted by rapturous crowds in the Chinese capital two days before it officially launches the Summer Games.

The arrival of the torch marks one of the final steps in China's seven years of preparations for the games that have cost billions of dollars, and one which Beijing hopes will serve as the country's symbolic debut as a modern world power.

The torch will tour Beijing before ending up at Friday's opening ceremony for the games. It will be carried by a diverse group, including China's first astronaut in space Yang Liwei, movie director Zhang Yimou and basketball superstar Yao Ming.

"I'm very happy to be here," said Yang before the relay kicked off from the Forbidden City, home of Chinese emperors since the 15th century.

"That the torch is finally in Beijing is a realization of a dream we've had for a hundred years," Yang said, minutes before he took up the flame as its first torchbearer.

Basketball star Yao Ming carried the torch out of China's symbolic Tiananmen Gate, below the portrait of Chairman Mao.

Overseas, the torch relay was disrupted by protests or conducted under extremely heavy security since it left Greece on March 24, turning an event that should have built up excitement for the games into something of a public relations disaster for the hosts.

The protests have mostly been in response to China's crackdown in March on anti-government riots in Tibet and to more general concerns over human rights issues in China.

On Wednesday, a pro-Tibet group said police detained four activists after they unfurled banners outside the Beijing National Stadium, site of the opening ceremony.

Three men and one woman from Students for a Free Tibet climbed two electricity poles in front of the stadium, dubbed the Bird's Nest, and unfurled the two banners at dawn, said Lhadon Tethong, the New York-based group's executive director.

One banner said "Tibet will be free" and the other said "One World, One Dream" — the slogan for the Beijing Olympics — with the words "Free Tibet" in Chinese.

After an hour, fire trucks pulled up and the protesters were peacefully led away by police and members of the internal security force, Tethong said.

"We have not had any contact with them because their phones are off," she said.

Sun Weide, the spokesman for the Beijing Olympics organizing committee, did not answer his telephone. Zhao Min, from the Beijing Public Security Bureau spokesman's office, said officials were trying to confirm the incident and had no immediate comment.