Shanghai police have cracked a group of terrorists who planned to attack a football preliminary venue in the Olympic co-host city.

"We have obtained information that international terrorist organizations would likely launch an attack against an Olympic venue in the city during the Games," said Cheng Jiulong, Shanghai Public Security Bureau deputy director and head of the Shanghai security office for the Olympics.

"We have staged raids and cracked a group of terrorists," he said.

Chen would not provide further details such as when the terrorists were detected, how many suspects were detained and where they came from.

"According to information we have obtained, the Olympic venue, athlete's apartments and routes leading to the venue are at a safe level now," he said. "But the threat of terror attack still exists."

Shanghai police have been put on a "crisis" footing as part of a campaign to ensure public security during Olympic football matches in the city next month.

"We have made adequate preparations for the football and are confident of ensuring safety during the Games," Cheng said.

He stressed security personnel must work with a "sense of crisis" and spare no effort to maintain law and order in the city.

Shanghai will host 12 Olympic football matches during the Aug. 8 to 24 Games.

Shanghai Stadium, the football venue, has been closed for security checks since July 20, with police and armed police conducting round-the-clock patrols.

Firefighters, engineers and medical staff will be deployed at the venue to guard against explosive, nuclear and biochemical attacks.

Random identity checks would also be conducted near the stadium and in heavily-congested commercial areas such as Xujiahui, he said.

Hu Shunkang, also of the municipal public security bureau, said surveillance cameras had been installed on 1,500 buses passing the stadium and extra security checkpoints were set up at airports and subway and rail stations.

Sales of explosives and toxic and radioactive materials were suspended from July 20 to Aug. 25. Civilian air traffic over the city would be halted during the football matches, Hu said.

The police also announced rewards ranging from 10,000 yuan (1,464 U.S. dollars) to 500,000 yuan for information on serious crimes.

"With our successful security maintenance experience in the meetings of APEC (Asia-Pacific Economic Cooperation) and the Shanghai Cooperation Organization, we are confident of ensuring a safe Olympics in Shanghai," Cheng said.

(Xinhua News Agency July 25, 2008)