The Hong Kong government made its check-in app mandatory for most adults in bars and restaurants on Thursday, the latest expansion of coronavirus tracing tech at a time of heightened privacy concerns in the city.

The international finance hub has kept infections at bay thanks to mostly closed borders, some of the world's strictest quarantine rules and ongoing social distancing rules. 

No local infections have been recorded in months, but the city is further ramping up virus measures, aligning with China's zero-Covid strategy as it seeks quarantine-free travel with the mainland.

From Thursday, all adults under 65 must use the city government's Covid app, scanning QR codes to log their presence at 18 types of premises -- including eateries, cinemas, gyms and karaoke venues.

The logs can be used to trace infections if there is an outbreak.

Children and the elderly were exempted at the last minute after a public backlash against the proposal to make the app mandatory for all.

The "Leave Home Safe" app has been in use since November 2020, but until Thursday, it was not mandatory and people could still fill out paper slips when entering venues.

Chum Tak-shing, a local district councillor in Sham Shui Po, said many older residents who are not exempted in his working-class district do not own, and cannot afford, a phone to run the app.

"(They) are now having to spend nearly HK$1,000 (US$128) on a smartphone and a new SIM card they don't necessarily need," he told AFP.

Febrile politics 

Coronavirus contact tracing has got caught up in Hong Kong's febrile politics as China cracks down on dissent in the city.

Despite assurances about data security from the authorities, concerns have swirled about how information collected by the app will be stored -- and how it may be used.

User information on Hong Kong's check-in app is currently linked to phone numbers, not names.

Mainland China, however, uses a tracing app that is linked to people's identities.

Last week, Hong Kong announced anyone wishing to travel to the mainland would need to download a version of that app.

Some restaurants and venues within Hong Kong's "yellow economy" -- businesses that supported the city's now dismantled democracy movement -- have often refused to use "Leave Home Safe" as a form of protest.

A number of them are considering going takeout-only to avoid using the app.

Oscar You, co-founder of local online delivery platform lingduck, told AFP that queries from eateries looking to sign on to his service had risen 30-40 percent ahead of the app mandate rollout on Thursday.