BEIJING – Shanghai police have broken up an international terrorist group that had planned to attack an Olympic football preliminary match in the city, state news agency Xinhua said on Thursday.

'We have staged raids and cracked a group of terrorists,' Xinhua quoted Cheng Jiulong, Shanghai Public Security Bureau deputy director and head of the Shanghai security office for the Olympics, as saying.

However, Cheng did not say when the terrorists were first discovered, how many suspects were detained or where they came from, said Xinhua.

'We have obtained information that international terrorist organizations would likely launch an attack against an Olympic venue in the city during the Games,' Cheng said.

The report comes after state media said earlier in the day that Chinese paramilitary police swore to prevent terrorist attacks or 'political incidents' from disrupting the Beijing Olympics in a show of force at the Games' main stadium.

'International terrorist forces are itching to strike with terror attacks against the Beijing Games, and hostile domestic forces' disruption and sabotage activities against the Games are steadily unfolding,' the People's Armed Police News reported.

Chinese officials have said their main Games security worries focused on separatist militants seeking an independent Uighur homeland in the country's far west Xinjiang region and campaigners for an independent Tibet.

Human rights critics say China has grossly exaggerated the security threats from Uighurs and Tibetans to justify harsh control in those regions.

Shanghai police have been put on a 'crisis' footing as part of a campaign to ensure public safety during Olympic football matches in the city next month, said Xinhua.

Shanghai will host 12 Olympic football matches during the Games and the stadium has been closed for security checks since July 20, with armed police conducting round-the-clock patrols, said the news agency.

Firefighters, engineers and medical staff would be deployed to the stadium to prevent bomb blasts and nuclear and biochemical attacks, it said.

(Reporting by Kirby Chien; Editing by David Fogarty)