Model planes, hot-air balloons and para-gliders will be under the ban from July 20 to September 24 imposed by the Municipal Commission of Education.

Besides, institutions and schools have been asked to keep these flying objects under safekeeping. Special personnel should be assigned to take care of flying objects collected from individual owners to prevent "unlawful elements" from carrying out sabotage or "staging political publicity", the municipal education watchdog said.

The authorities also told various units and educational institutions to be on alert and report the cases of violation during the ban, official Xinhua news agency said.

The ban came a day after the organisers issued the Olympic venue rules yesterday that prohibit carrying of banners and flags larger than two metres by one metre, flags of non-participating members as well as sit-ins and demonstrations among others.

China's ruling Communist Party's official mouth piece, People's Daily, said the international situation and the political environment are "becoming increasingly complicated by the day, and the dark clouds of terrorism on our borders a fact that cannot be ignored."

Beijing has termed terrorism as the biggest threat to the Olympics. China had recently conducted national-level anti-terror drills in Beijing and co-host cities -- Shanghai, Tianjin, Qinhuangdao, Shenyang and Qingdao.