The warning issued in a document Thursday did not specify the punishment to be levied.

The apps in question are the Vietnam Health Declaration app along with tokhaiyte.vn, the Bluezone app and the NCOVI app. Among other functions, these help users make medical declarations, record close contacts between app users and record instances of them having been to public locations.

The document says that people doing business or frequenting entertainment venues, offices, factories, gyms and other meeting places, hospitals, schools and malls, as also those using public transport should have contact tracing apps installed on their phones.

It specifies that people who go to public places and locations with large gatherings need to install Bluezone and turn on the Bluetooth function so that the app records users’ close contacts.

Those in quarantine or being medically monitored must install the Vietnam Health Declaration app and an app to track close contacts.

The ministry has asked local administrations to "punish" those who possess smartphones but fail to comply with the above-mentioned requirements.

Over a month into the fourth Covid-19 in Vietnam, the most challenging one yet, the nation has recorded 4,357 domestic cases in 36 of its 63 cities and provinces.

Bac Giang Province and its neighbor Bac Ninh account for a majority of the infections, with 2,297 and 857 cases, respectively. Meanwhile, the rising number of infections in HCMC associated with multiple clusters, with 208 cases recorded so far, has prompted the southern metropolis to begin a two-week social distancing period starting Monday.