China is leaving nothing to chance remaining on high alert against possible attempts to sabotage Olympics to which terrorism has been identified as the biggest threat.

The reminder comes as some people might not pay attention to daily items listed on tickets along with other illegal items including explosives banned from the Olympic venues, state-run Xinhua news agency said.

After national-level anti-terror drills conducted in Beijing and co-host cities Shanghai, Tianjin, Qinhuangdao, Shenyang and Qingdao - the Chinese authorities have stretched security to more detailed aspects like long umbrellas and handbags coming under checks.

A three-month campaign was launched in June for checks at Beijing subway which carries millions of passengers every day.

More than 3,000 inspectors at 93 metro stations are conducting searches for dangerous articles, including guns, ammunition, knives, explosives, flammable and radioactive materials and toxic chemicals.

Liquids would also be checked, unless the passenger takes a drink in front of inspectors.

Strict security is also in force at the iconic Tiananmen Square, the worlds largest square, a political symbol as well as a popular tourist spot.