Videos posted by local media show a row of cubicles, each with a timer above the door. The display indicates when a cubicle is occupied and for how long.

The displays were spotted at lavatories in the Yungang Buddhist Grottoes in the city of Datong, Shanxi Province.

But according to a longtime China expat, the timers have also appeared in Shanghai.

Christian Petersen-Clausen, a documentary maker, said: “First time I’ve seen these digital clocks that announce how long each of these bathroom stalls have been occupied. Seen in a park in Shanghai.”

While many have decried the timers as yet another example of overreach by the government into people’s private lives, others say they might stop the nuisance of people hogging public lavatories to scroll on their phones.

The Yungang Buddhist Grottoes is a Unesco heritage site, with tens of thousands of huge statues cut into caves in the mid-fifth century to early-sixth century AD. Last year it had 3 million visitors, according to official data.

The timers were flagged to the Xiaoxiang Morning Herald by a visitor who said they found them embarrassing.

“I found it quite advanced technologically so you don’t have to queue outside or knock on a bathroom door,” the paper quoted the visitor as saying.

“But I also found it a bit embarrassing. It felt like I was being monitored.”

A staff member at the attraction told the newspaper that the timers had been installed to cope with an increase in the number of visitors, but stressed they were not imposing a limit.

“They aren’t there to control the durations you could use the bathrooms,” they said.

“It’s impossible we would kick someone out midway. And we aren’t setting a time limit, such as five or 10 minutes, of how long one could use the toilets.”