In response to a recent COVID-19 flare-up, Beijing sealed off a large downtown mall and locked down several residential communities on Thursday, as the latest nationwide wave spread to the capital’s central districts.

The most recent spike occurred as a sensitive three-day meeting of top Communist Party leaders in the capital ended.

China has largely stopped the spread of COVID-19 through snap lockdowns, mass testing, and travel restrictions, but authorities are on high alert following a nationwide spike in local outbreaks linked to domestic travel in the last month.

Six new cases were discovered Thursday morning in the central districts of Chaoyang and Haidian, according to local media, all of which were close contacts of people infected recently in northeastern Jilin province.

Raffles City Mall in central Beijing’s Dongcheng district was closed down on Wednesday evening after a person with COVID-19 was discovered to have visited the mall, according to the Beijing Youth Daily.

Exits were closed, and no one inside, including staff and customers, was allowed to leave until they were tested.

The mall was still closed on Thursday.

Four residential communities, a primary school, and an office compound were placed on lockdown early Thursday, preventing tens of thousands of residents from leaving and forcing them to undergo mass testing.

Staff in hazmat suits piled up bags of food for residents trapped inside, according to livestream footage of the areas under lockdown on local media.

According to local health officials, four of the diagnosed cases are members of the same household, while the two remaining cases are a Jilin resident on a business trip to Beijing and their close contact.

While more countries around the world begin to relax virus controls, China has maintained a strict zero-tolerance COVID-19 strategy that has kept its international borders largely closed since the pandemic began last year.

Millions have been placed under lockdown, and domestic travel rules have been tightened, with many planes and trains cancelled as a result of the latest wave.

By the end of the year, China expects to have achieved 80 percent vaccination coverage.