Tourist authorities in China's capital have started using facial recognition technology to limit how much toilet paper a person can take in public facilities.

The unusual move - part of a "toilet revolution" - is another step in China's vast upgrading of public facilities.

Toilets at tourist sites, notorious for primitive conditions and nasty odours, are a special focus of the campaign, a response to a vast expansion in domestic travel and demands for better quality facilities from a more affluent public.

Zhan Dongmei, a researcher with the China Tourism Academy, said: "Today in China, people are highly enthusiastic about tourism, and we have entered a new era of public tourism. The expectation of the public for the toilet is becoming higher."

At Beijing's 600-year-old Temple of Heaven, administrators recognised the need to stock public toilets with paper, a requirement for obtaining a top rating from the National Tourism Authority, but they needed to prevent patrons from taking paper away - hence the introduction of technology that dispenses a single 2ft length of paper every nine minutes after a face scan.

"People take away the paper mostly because they are worried they can't find any when they want to use it the next time. But if we can provide it in every toilet, most people will not do it any more," Mr Zhan said.

Launched two years ago, the revolution calls for at least 34,000 new public toilets in Beijing and 23,000 renovated by the end of this year.

Authorities are also encouraging the installation of Western-style sit-down commodes rather than the more common squat toilets. Around 25 billion yuan has already been spent on the programme, according to the National Tourism Administration.

Mr Zhan said the ultimate target is "to have a sufficient amount of toilets which are clean and odourless and free to use".

At Happy Valley, the largest amusement park in Beijing, around 4 million annual visitors rely on 18 toilets, each of which is assigned one or two cleaners who must make their rounds every 10 minutes on busy days.

"People come here to have fun, but if the toilets are disgusting, how can they have a good time here?" said vice general manager Li Xiangyang. "It is the least we should do to offer a clean and tidy environment for tourists to enjoy both the tour of the park and the experience of using our toilets."

Going a step further, the financial hub of Shanghai opened its first gender-neutral public toilet in November to boost convenience and efficiency.

Mr Zhan said the toilet revolution is about 90% complete, but warned: "We can't accept the situation that a lot of investments have been made to build toilets and they turn out to be unsanitary and poorly managed."