Restrictions on the sale of radio-controlled helicopters and planes have been imposed in Beijing as China heightens security before a once-in-a-decade leadership change, state media said Wednesday.

For some models of helicopters and planes -- which can only be guided within a few metres -- purchasers must prove their identity to the shopkeepers, Beijing's Youth Daily reported.

Other shops have been ordered to suspend selling the toys altogether, the newspaper said.

The clampdown comes amid a tightening of security as the Communist Party prepares for a pivotal handover of power which is set to commence at the 18th Party Congress, which starts in Beijing on November 8.

A total of 1.4 million volunteers have been mobilised to help safeguard the highly-anticipated gathering, the state-run Xinhua news agency reported.

Beijing has also put pressure on government critics ahead of the meeting.

Activist Hu Jia was forced to leave the capital and go to his family's home town in the eastern province of Anhui until the congress ends, New York-based Human Rights Watch said.

Domestic media have also reported an increase in identity checks across public transport in Beijing.

Security officials have carried out increased surveillance on trains from the restive mainly Muslim northwestern region of Xinjiang, domestic reports said.

The issue has been discussed by netizens on China's hugely popular micro-blogging websites.

One poster on Sina Weibo, China's version of Twitter, said he was required to fill out a form when he got into a taxi, detailing his personal information and where he was going.

Another netizen said he was not allowed to buy a knife because of restrictions before the congress.

The tightly scripted meeting will last about one week, and will see the unveiling of a new politburo that is expected to see Vice President Xi Jinping promoted to Communist Party general secretary, in place of Hu Jintao.