China is enforcing lockdown restrictions in areas around Beijing more intensively, and will mass test the nearby port city of Tianjin, stepping up its quest to wipe out COVID-19 ahead of a key meeting of the Communist Party’s top leaders.

The moves come even as officials seem to be getting the national case load under control, with 1556 new infections reported in the community for Sunday. Despite the progress, the country remains focused on eliminating transmission of a virus that most of the world has now accepted as endemic.

Shijiazhuang, the capital of Hebei province bordering Beijing, confined residents of four major downtown districts to their homes for three days from Sunday afternoon, saying a mass testing exercise would be undertaken. The city of some 11 million also suspended subway services and halted non-essential business operations in the locked-down districts. The province, home to many workers who commute to the Chinese capital, reported 45 COVID cases for Sunday.

The partial lockdown of Shijiazhuang follows the imposition of restrictions elsewhere in Hebei last week. Zhuozhou city bordering Beijing has been in lockdown since Tuesday, while Xianghe county issued a stay-at-home order for its 384,000 residents from Friday after finding just one unconfirmed case, going beyond the guidelines stipulated in the country’s recently reviewed COVID playbook.

Hebei’s response suggests a higher level of sensitivity around the capital, as Beijing prepares to host the party congress, a once-in-five-years meeting where President Xi Jinping is due to secure a precedent-breaking third term in office. Xi has made the COVID-zero policy a key tenet of his rule, saying it’s avoided the massive death tolls of places like the US, despite the disruption caused.

Concern about the restrictions in Shijiazhuang are growing on social media, however, where several users posted information saying the city would use patrol officers and drones to ensure people were abiding by the stay-at-home orders and detain those who weren’t.

An outbreak in Tianjin, some 30 minutes by high-speed train from Beijing, prompted authorities to order a citywide mass test, according to state television. The port hub had reported 31 local COVID cases for Sunday. The capital itself reported one infection.

China is holding fast to COVID-zero, even as more infectious variants require increasingly stringent restrictions that are upending growth and business activity. Lockdowns and other curbs are hitting the world’s second-largest economy, with the slowdown deepening in July. Retail sales, industrial output and investment have all missed economist estimates. Profits at industrial firms in China fell in the first seven months of the year, data on Saturday showed.