China on Wednesday enforced a lockdown in Xian, home to 13 million people after the city reported the first cases of a new Omicron subvariant.

The lockdown was implemented after Xian reported 18 COVID-19 infections from Saturday to Monday, all of which are of the Omicron BA.5.2 subvariant, according to local disease control officials, reported CNN.

BA.5.2 is a sub-lineage of BA.5, which is already dominant in the US and appears to escape antibody responses among both people previously infected with COVID-19 and those who have been fully vaccinated and boosted, according to researchers.

It is the first time the subvariant has been reported in China, one of the last places in the world still adhering to a stringent zero-Covid policy.

On Tuesday, Xi'an officials announced sweeping restrictions that would shut down parts of the city for seven days starting from Wednesday.

Entertainment, sports and cultural venues, including bars, cinemas, gyms, libraries and museums, were closed; restaurant dining and large gatherings, from weddings to conferences, were suspended; all places of worship were shut and religious activities banned, city official Zhang Xuedong said at the press conference Tuesday.

Kindergartens and primary and secondary schools were ordered to start summer holidays early, while universities were told to seal their campuses, according to Zhang.