The fourth and final phase of Olympic ticket sales to the domestic public began on Friday morning with 820,000 tickets on offer.

The Games ticketing center said only tickets for competitions taking place locally would be available for purchase. That meant Beijing citizens could only buy 250,000 tickets for competitions in the capital area.

Thousands in Beijing had been lining up at ticket booths since Wednesday noon.

To give more people a chance to watch the Games and prevent scalping, organizers had stipulated that only two tickets per session would be available for purchase each time.

The line extended for more than two km at the ticket booth near the Bird's Nest.

"The Olympics finally comes to China. I cannot afford to miss the opportunity!" said a woman surnamed Wang. The 67-year-old bought two tickets, one for a diving session in the Aquatic Center, aka the "Water Cube," and the other for baseball in Wukesong venue.

Although mid-day temperatures peaked at 34 degrees Celsius, people would not leave for a break. Ambulances stood by for emergencies.

Local police have detained 60 suspects for scalping Olympic tickets in the past two months, a Beijing Municipal Public Security Bureau spokesman said on Thursday.

The suspects, apprehended since May 5 when the third phase of domestic ticket sales started, were accused of reselling the tickets at inflated prices of up to 100 times the face value, the spokesman said.