BEIJING, August 8, 2008 (AFP) - China's once-in-a-lifetime Olympic dream became reality Friday as the Beijing Games opened with a dazzling ceremony showcasing the nation's ancient civilization and an offer of friendship to the world.

The political controversies and pollution concerns that plagued the run-up to the Games were swept aside, at least briefly, as 91,000 people at the iconic 'Bird's Nest' stadium bathed in the colour and excitement of the night.

Billions of people around the world tuned in to watch the spectacular show, an event that had been hyped as a coming out party for a nation whose global power is rising as quickly as its wealth.

'If you are Chinese, you have to be here. This is a 100-year dream come true,' said Luo Rensi, 83, one of thousands of Chinese fans who congregated outside of the Olympic venues after being unable to get a ticket.

'China has been through some bad times during my long life, but this is truly the best time.'

The ceremony began at 8:00 pm (1200 GMT) on the eighth day of the eight month of 2008 -- a tribute to the number 8 that many Chinese deem lucky as it represents prosperity.

Those inside were treated to a 50-minute extravaganza masterminded by acclaimed Chinese film director Zhang Yimou, which involved 15,000 performers, a kaleidoscope of fireworks and the thunder of ancient drum beats.

The show celebrated some of China's greatest inventions -- the compass, gunpowder, paper and printing -- as well its ancient art and the magnificence of the Great Wall.

It concluded with a focus on unity in the modern world, with the final moments seeing performers on a giant elevated globe and a theme song entitled 'You and Me'. The traditional parade of athletes then began amid huge cheers.

For China, the 16-day Games are an opportunity to show the world how far it has come since the communists came to power in 1949 following a brutal civil war -- particularly in the past three decades of its historic development.

During the seven years since Beijing won the right to host the Games, roughly 40 billion dollars has been spent building the venues, expanding transport networks, upgrading other infrastructure and creating parks.

But the Games risks equally being remembered for the controversies that overshadowed much of their build-up, including China's rule of Buddhist Tibet and Muslim Xinjiang, its human rights record and darker aspects of its foreign policy.

Pro-Tibet campaigners and rights activists have been protesting around the world this week to further pressure China's communist rulers.

Up to 150 saffron-clad Tibetan monks tried to storm the heavily guarded Chinese embassy complex in New Delhi on Friday as the opening ceremony got underway.

And US President George W. Bush, who was one of dozens of world leaders who attended the ceremony, earlier spoke out for freedoms, continuing a series of comments in recent days to pressure China on human rights.

'I strongly believe societies that allow the free expression of ideas tend to be the most prosperous and the most peaceful,' Bush said at the opening of the new US embassy in Beijing.

China has repeatedly insisted that politics should play no part in the Games, although President Hu Jintao defended his nation's honour in regards to the Olympics.

'The Chinese government and people have seriously implemented the solemn commitments made to the international society since Beijing won the Olympic bid in 2001,' Hu told an audience of world leaders including Bush ahead of the ceremony.

Further highlighting the tension lurking behind the opening ceremony, authorities enforced sweeping security measures across Beijing and other parts of the country on Friday.

More than 100,000 security forces were called in to scout for any trouble in the city and Beijing airport was temporarily shut down just ahead of the start of the ceremony, amid warnings of terror attacks from Islamic separatists.

The Chinese government is also acutely concerned that the Games could be marred by peaceful protesters, whether they be Chinese seeking address against official injustice or foreign activists.