(Adds relay underway, details, background)

By James Pomfret

HONG KONG, May 2 (Reuters) - Eight protesters were detained briefly in Hong Kong and another pro-Tibet activist was jostled and derided as a traitor on the first leg of the Olympic torch's China tour after becoming a beacon of controversy around the world.

Security around the flame was tight on Friday, with roads closed, crowds kept at a distance, and at least 16 Chinese security guards in blue and white track suits and police on motorcycles alongside the torch bearers.

Authorities in the former British colony have drawn criticism for taking an uncharacteristically tough line including blocking several people from entering the city, among them three pro-Tibet campaigners and a Danish artist and rights activist.

The torch's 20-nation journey has been dogged by protests, mostly over China's human rights record and Tibet, which have deeply embarrassed Beijing and provoked retaliatory rallies at home and abroad by patriotic Chinese.

Many in China will no doubt be breathing a sigh of relief that the international leg is finally behind the flame as it embarks on a domestic leading up to the Aug. 8 opening ceremony in Beijing.

"It is a great and solemn honour for Hong Kong, Asia's world city, to welcome back the Olympic flame on behalf of our proud nation," Hong Kong leader Donald Tsang said at the relay's start.

But the protests and trouble continued on Friday. Pro-Tibet supporters were joined by democracy protesters and activists demanding a truthful account of the crackdown on pro-democracy protesters at Tiananmen Square on June 4, 1989.

TROUBLE

As the relay started under an overcast sky, police prevented demonstrators calling for religious freedom in China from raising a Tibetan flag on a street where the torch would pass and led the eight protesters to a van. They were later released and told they had been taken away for their own safety.

Another man holding a placard urging dialogue between the Chinese government and the Dalai Lama was surrounded by bystanders who heckled him with profanity, pushed him around, called him a traitor and said he was "mentally sick".

"I was just expressing my opinion. What right do they have to treat me like this? They are uncivilised!" said the man, 72-year-old cab driver Ng Pun-tuk.

Debby Chan, of the Tiananmen Mothers campaign, said: "We also support the Olympics, but we just want to make the additional point that China must live up to its human rights promises."

In Kowloon, near where the torch relay started, about 25 democracy protesters and a large group of Chinese students faced off in a shouting match as police kept watch.

SUPPORT FOR THE MOTHERLAND

Chinese university students waved national flags in front of the protesters' banners, and shouted and sang the national anthem to try to drown out the calls for democracy.

"We are here peacefully to express our ideals that we love China and the motherland," said one, named Yu Xiang.

In Paris and London, the torch was a target for protests by rights and pro-Tibet demonstrators who, in several cases, lunged at the flame, even grabbing it, and tried to douse it with water.

Chinese living abroad turned out in force for later runs, creating controversy of their own.

In the United States, conservative and liberal members of Congress joined forces to urge a U.S. government boycott of the opening ceremonies of the Beijing Games, which start in August, accusing China of gross human rights violations.

American actress Mia Farrow entered Hong Kong on Thursday to call on China to do more to end the violence in the troubled Darfur region of Sudan. She was questioned by immigration authorities before being allowed into the city and was told torch relay disruptions would not be welcome.

The Hong Kong Journalists Association and other human rights advocacy groups condemned the curbs and blamed Beijing's invisible hand for tainting the city's free and open image. Hong Kong has been under Chinese rule since 1997.

After Hong Kong, the torch goes to the Chinese gambling hub Macau and then starts its journey through the mainland. A sister flame is awaiting good weather to summit Mt. Everest. (Writing by John Ruwitch; Editing by Jeremy Laurence) (Take a look at the Countdown to Beijing blog at http://blogs.reuters.com/china)

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