Police in Shanghai have cracked a terrorist cell planning to attack an Olympic football venue in the Chinese financial hub.

Australia's Olyroos are to play their first two matches of the Olympic Games at the venue.

"We have obtained information that international terrorist organisations 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."

Chen would not provide details about when the terrorists were detected, how many suspects were detained or 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 will host 12 Olympic football matches during Games with the Olyroos to play Argentina and Serbia in the city.

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

Police had been placed on a "crisis" footing as part of efforts to ensure public safety in the city, the report said.

Random identity checks would be conducted near Shanghai Stadium and in other well-travelled parts of the city in the lead-up to the Games, Xinhua quoted Cheng as saying.

He said security personnel should "spare no effort to maintain law and order in the city," the report said.