Paramilitary policemen move into position during an anti-terrorism drill on Beijing [GALLO/GETTY]

The authorities have expressed their concern that some ticket holders "might not pay attention'' to the list of items banned from Olympic venues, which also includes cigarette lighters, beverages, and all toxic or potentially flammable materials.

"As long as there is a security risk, security personnel get to remove it,'' the official Xinhua News Agency reported.

The reminder follows reports of stepped-up security to guard against attempts to sabotage the games.

Reported threats with no proof

Beijing claims Tibetan forces allied with the exiled Dalai Lama and Islamic separatists from the northwestern Xinjiang region are seeking to torpedo the games with violent plots, including suicide bombers.

Although no evidence has been provided to support such claims.

Authorities have accused Xinjiang separatists of attempting to crash an airliner in March and planning to kidnap athletes and journalists during the games, which start August 8.

Xinjiang, like the similarly troubled region of Tibet, has a language and culture that is distinct from that of China's ethnic Han majority.

Extremists among Xinjiang's indigenous Uighur ethnic group have waged a low-intensity struggle against Chinese rule for decades.

Many have been sentenced to long prison terms or death on separatism charges.

Chinese policemen march past the Potala Palace [GALLO/GETTY]

Increasingly tight security has been imposed throughout China as the games approach, with new security checks implemented in Beijing's subway and on
iconic Tiananmen Square, the scene of student-led pro-democracy protests in
1989 that were brutally crushed by the military.

China plans to deploy about 100,000 anti-terrorism police during the games, with some of Beijing's 500,000 Olympic volunteers also serving in security roles.

Underscoring the thoroughness of the measures, ground-to-air missiles have been installed just 800 metres from the National Stadium where the opening and closing ceremonies will be held.

Xinhua also announced a blanket ban beginning July 20 on visitors to prestigious Peking University, site of the Olympic table tennis events.

Given China's tightly controlled society, security experts do not consider terrorism a major threat to the games, although concerns persist over the likelihood of nonviolent protests.

Press freedom

The biggest challenge China has faced thus far is from bad publicity as a result of repression against political dissidents and the media.

Hein Verbruggen, the senior International Olympic Committee official who has
guided preparations, said Tuesday it was time for Beijing to deliver on its
commitment to allow media to report freely during the games.

The IOC and television rights holders such as America's NBC have been at odds for months with Chinese security officials, fighting to clarify the rights of satellite trucks to move freely around the city of 17 million.

Access to spots like Tiananmen Square, who will be allowed in, when and under what conditions, is also a contentious subject with Chinese authorities fearing the site could be used as a TV backdrop by pro-Tibet protesters or the Falun Gong spiritual movement.