The Olympic cauldron took the form of a huge torch, in a break with tradition

China has presented a dramatic display of fireworks, music and dancing to mark the opening of its Beijing Olympics.

Some 10,000 performers took part in the ceremony, watched on TV by an estimated one billion people, before athletes paraded around the national stadium.

Security was tight in the capital, and three US activists were arrested after holding a pro-Tibet protest. Larger rallies took place in Nepal and India.

Analysts say it is the most politicised Games since the Cold War era.

The build-up to the event was dogged by worries over pollution and criticism of China’s rights record.

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Beijing has faced pressure to improve civil liberties – with US President George W Bush among several world leaders to express concern over a crackdown on dissidents.

But after the controversy of the run-up, the opening ceremony certainly changed the focus of attention.

Some 90,000 fans packed the new national stadium – known as the Bird’s Nest because of its steel lattice construction – and cheered the performers.

The choreographed show took seven years to plan, and costs are estimated to have hit a record-breaking $40bn (£20bn).

It began at eight minutes past eight on the evening of 8 August, reflecting the belief widespread in Asia that eight is a lucky number.

More than three hours later, China’s President Hu Jintao officially declared the Games open.

And in a theatrical finish to the day’s activities, champion gymnast Li Ning was winched up to the rim of the stadium carrying the Olympic torch – the end of its journey around the world.

He used the torch to light the Olympic cauldron – in the form of another huge torch – and an explosion of fireworks ensued.

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The Beijing Olympics opening ceremony gets off to an impressive start

Bomb threat

Meanwhile, security has remained a pressing concern for the Chinese authorities.

An extra 100,000 troops and police have been deployed in the capital. Areas including Tiananmen Square – which could provide a rallying point for protesters – were closed off.

In other developments:

Beijing pollution: Facts and figures

• Three US activists were detained while trying to mount a pro-Tibet protest near the national stadium, according to the Associated Press.

• A protester tried to set himself alight outside the Chinese embassy in the Turkish capital Ankara, as Chinese Muslims protested against alleged rights violations in China.

• An Air China flight bound for Beijing from Tokyo was forced to turn back after an Olympic-related bomb threat was received.

• Exiled Tibetans held angry protests in Nepal, with hundreds reported to have been arrested in the capital, Kathmandu.

• Hundreds of Buddhist monks tried to storm the Chinese embassy in Delhi, India, in protest at Beijing’s Tibet policies.

Weather worries

Pollution remains a key concern for the Games and on the morning of the opening ceremony, fog obscured the Beijing skyline.

A BBC reading suggested air quality remained below World Health Organization (WHO) standards.

But Guo Hu, director of the Beijing Meteorological Observatory, predicted that heavy rain over the weekend would clear the skies.

And he warned that hazy conditions should not be confused with high levels of pollution.

On Thursday, International Olympic Committee President Jacques Rogge said events that lasted more than an hour could be shifted or postponed if the pollution was bad.

But he also praised China’s “extraordinary” efforts to cut pollution ahead of the Games, saying there was no danger to athletes’ health.