Despite heavy security presence outside the 'Bird's Nest' stadium and 'Water Cube' aquatics centre, chaos erupted at about 4.30am when a 2,000-strong crowd tried to break through control barriers to get to the ticket counters after seeing lights go on in one of the windows.

'I was sleeping but got awakened by a loud cry,' said Sui Xu, an 18-year-old high school student. 'Then I saw people swarm and push ahead like waves. I had no idea what was going on but I ran with the crowd nonetheless - to keep my spot in the queue.'

Public security officers were unable to contain the crowd, with people screaming, shoving and scrambling in panic. Order was gradually resumed when armed police were sent in half an hour later.

More disturbances occurred when disputes broke out between tired and frustrated fans, and queue-jumpers tried to steal a spot on the line. And in an attempt to ease the situation, officials split the queue but in the process caused a stampede as those towards the rear to raced to get to the front of the new lines.

When ticket sales kicked off at 9am, layers of security forces tried to organise people into small groups, letting 40 people in at a time.

Many in the crowd were upset about the lack of organisation and basic information on where to line up and how to buy tickets. Some complained that when they turned to police for information they were simply told to go away.

At about 10.30am, scuffles broke out between Hong Kong journalists and police, who tried to stop the press from covering the chaotic scenes. Television footage showed several journalists being manhandled by police officers.

Xinhua reported that 30,000 people lined up for tickets and some became impatient because of the hot weather and long wait. Some journalists were escorted away after going into areas that were off limits, it said.

South China Morning Post photographer Felix Wong Chi-keung was taken away by police for allegedly kicking an officer, Xinhua said. He was released in the afternoon after expressing regret for inadvertently hurting the officer while he was being dragged away by police.

Hong Kong Cable TV footage showed dozens of people being dragged from the lines by police and one officer putting his arm around the neck of a Cable TV reporter and pulling him to the ground.

A police spokesman acknowledged it was 'chaotic and difficult' to maintain order. 'Demand was so high and too many people came at once so we ran into some security problems,' he said.

Bocog spokesman Sun Weide said the stampede was caused when ticketing officials tried to ease the discomfort of those in line by opening more sales windows.

However, the attempt to speed up the queues backfired.

Additional reporting Zhuang Pinghui and Peter Simpson