Japan [Images] called for calm but braced for trouble with tight security on Friday, as low-key protests began ahead of its leg of the Olympic torch relay, following emotional scenes at other venues around the world.

The global torch relay ahead of the Beijing [Images] Games in August has provoked protests against China's rights record, especially in Tibet [Images], as well as patriotic rallies by Chinese who say the West has vilified Beijing unfairly.

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The flame is meant to transmit a message of peace and friendship, but its journey has been largely turned into a political event and the torch has been granted the sort of security usually reserved for state leaders.

Chief Cabinet Secretary Nobutaka Machimura called for calm ahead of Saturday's relay in the central Japanese city of Nagano, a former Winter Olympics [Images] site.

"I hope this torch relay will take place peacefully in an atmosphere where everyone can celebrate," he told a news conference in Tokyo.

In Hanoi, Vietnam state-run radio reported that a US citizen of Vietnamese origin had been expelled on accusations of planning anti-Chinese protests at next week's Olympics torch relay in Ho Chi Minh City.

Reclusive North Korea, for its part, vowed to "astonish the world" with pomp, ceremony and safety during its stage of the relay on Monday, Chinese state media reported.

"North Korea has fully prepared an Olympic Games torch relay in Pyongyang that will be high-quality, outstanding, safe and successful," China's official Xinhua news agency cited a North Korean official as saying.

RIGHTWING TRUCKS, PRO-TIBET BANNERS

The flame's arrival in Nagano was greeted by right wing activist trucks roaming the streets, displaying huge Japanese flags and blaring "go away".

Yellow T-shirt-clad supporters of the Falun Gong religious group, outlawed by Beijing, marched down a Nagano street with a brass band and yellow banners.

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Dozens of people carrying pro-Tibet and Japanese flags later marched near the City Hall, blaring "Nagano City, cancel the torch relay now" as two vans of riot police trailed them.

"It's an embarrassment for Japan. To host the torch relay is the same as supporting oppression in Tibet," said Atsushit Matsuoka, 37, who worked for a publishing company.

Kunihiko Shinohara, head of Nagano's relay organising committee, tried to reassure ordinary Japanese who would be taking part in the relay. "I know some of you are worried, but we will do our best to ensure safety," he told them.

The torch will be guarded by up to 4,000 police, media said, with riot police and another 100 regular officers set to shield torch-bearers in two rows, shrouding the runners from sight.

They will be joined by two Chinese "flame attendants", although Japan has made it clear that their participation in security would not be welcome after criticism of the paramilitary guards as heavy-handed in protecting the torch elsewhere.

SPECTATORS BARRED

Spectators will be barred from the opening and closing ceremonies on Saturday in Nagano.

"The people of Nagano were so looking forward to cheering on the relay, but everyone is disappointed because no one will be able to see it," said Nagano taxi driver Michie Higuchi.

About 2,000 Chinese students from across Japan are expected to travel to Nagano carrying Chinese and Japanese flags and wearing matching T-shirts to show support for the relay.

More than 560,000 Chinese nationals live in Japan, official figures show, making them the second largest group of non-Japanese after Koreans. Many are students.

Pro-Tibet groups were to hold a prayer service early on Saturday for all those killed in recent unrest in Tibet before the relay on Saturday at the historic Zenkoji temple, which earlier withdrew as the kick-off site for the event.

The pro-Tibet groups would then congregate for a peaceful protest near the relay.

China has called the global torch relay a "journey of harmony" but the flame has become a magnet for anti-China protests. In London [Images], Paris and San Francisco, torch bearers were jostled by anti-Beijing protesters as they ran.

The demonstrations stirred nationalistic sentiment in China, and prompted calls from some Chinese to boycott foreign businesses. In the last leg in Canberra, more than 10,000 Chinese Australians staged a huge pro-Beijing rally.

The International Olympic Committee's athletes' commission said in a statement it is saddened the torch relay has "not had the peaceful passage it deserves".