A military veteran is not letting the aches and pains of old age get in the way of his desire to keep the streets of an ancient Chinese city pristine.

Zeng Ming, 92, goes about his work with all the stoicism and dedication of a soldier on that most tedious of tasks - guard duty.

A couple of years ago, duty called yet again and he signed up for the civilian service, not realizing at the time that his new adversary would be cigarette butts and that the streets of Xi'an, Shaanxi province, would be his new field of battle.

"One day, I bumped into sanitation workers picking up cigarette butts from the street and asked if I could help them," Zeng said.

Not long after, he took delivery of his weapons: a red bucket and a stick with pincers at one end.

Now, for two hours every day - an hour in the morning and another in the afternoon - the long-retired warrior picks up cigarette butts.

However, not content to wage this war alone, Zeng has made a name for himself as he urges locals and tourists alike to do their bit to support a campaign started in December 2016 to spruce up the city's image.

All they need to do, he said in material posted online, is to bend down and pick up any cigarette butts they come across on the streets.

Of course, dedication does not always trump the frailties of age, and his daughter once tried to persuade him to stop after he fell down one snowy day when picking up litter.

"These days his eyes and ears don't function that well, and I worry that he may have more accidents," she said.

However, his daughter's concern did not go down well with the elderly man, and for days he refused to talk to her, she said. In the end, she gave in to his perseverance. "As long as he feels happy," she said.

Even if Xi'an has many people who are careless with their litter, it is also fortunate to have many who are kind enough to be on the lookout for Zeng's welfare when he is on duty. Sometimes people rush to hold him before he prepares to bend down, he said.

And he must have a stern look, because many litterbugs who come across him quickly realize their mistake and pick up their rubbish.

"The appearance of a city is like the face of a man," Zeng told local media, adding that his daily regime is good for both the public and for his health.

Xi'an, the capital of 13 dynasties for over a millennium, is a major tourist destination, but one that also struggles to fight litter.

The city's Party secretary, Wang Yongkang, once picked up 27 cigarette butts on its ancient walls. That was one of the inspirations behind the idea of improving tourism and investment by promoting civic-mindedness among the public.

By the end of last year, the local government had organized about 700 promotional activities to fight littering, according to the urban management bureau.

It installed about 12,000 additional rubbish bins as well as 10,500 devices meant to extinguish cigarettes in order to reduce smoke pollution.

"It's not just about environmental and sanitation considerations, but it also demonstrates a city's ability to work effectively and efficiently using the right regulations," retired resident Chen Youliang told local media.

Kang Lifeng, deputy director of the Xi'an tourism development committee, told China Daily that the city also boasts the country's first online toilet map, which was developed last year with internet giant Baidu.

Visitors can click an app and select locations to check for nearby toilets. It shows about 450 facilities with a single search, and the total is expected to reach 1,000 by July, he said.

The government also provides subsidies to encourage more hotels to make their restrooms available to the public.

Xi'an aims to build more than six toilets per square kilometer, compared with the country's standard of three toilets per square kilometer. By 2020, the number of public toilets is expected to rise from 2,841 to a little more than 5,000, the Xi'an urban management bureau said.