China has ruled out any relaxation of cross-border policies, citing Covid-19 surges at home and overseas as it battles the worst outbreaks since the start of the pandemic. Stricter control measures have also been introduced in the capital Beijing , where schools were told to start the May Day holidays one day earlier to participate in mass testing and avoid on-campus transmission. This came as the southern city of Guangzhou ordered mass testing for all residents in seven districts, after routine screening for airport staff returned positive results from three employees and a family member on Wednesday night. Most flights were cancelled as the Baiyun airport was placed under “effective control”. And while some flights within China resumed after 2pm on Thursday, a later announcement grounded all domestic flights for the next two days. Meanwhile, National Immigration Administration spokesman Chen Jie said its “strict and tight” border policy would continue. The NIA would resolutely play its official role in the “dynamic zero” strategy against Covid-19, with strict border controls aiming to prevent virus imports, Chen said, according to a statement following a closed-door media briefing late on Wednesday. “Immigration management agencies at all borders will continue to maintain the highest level of prevention and control,” he said. China pledges ‘strictest, most resolute’ measures to halt Omicron spread While China’s political centre Beijing resorts to drastic measures to try and stop infections at an early stage, its financial heart Shanghai has been in lockdown for more than a month. At least 15 Chinese provinces have also recorded local infections in recent days. Beijing responded swiftly to a small outbreak of six cases last Friday, ordering almost citywide mass testing and aiming to complete three rounds by Saturday. The first round picked up 12 positive samples and the second round had already returned seven positive results in Chaoyang district by Thursday afternoon, according to district deputy chief Yang Beibei. The outbreak in Beijing comes just months before the city hosts the 20th Communist Party Congress , with a major power reshuffle on the cards and party secretary President Xi Jinping expected to earn an unprecedented third term. China’s handling of the pandemic is seen as a key part of the legacy of both Xi and the party. A Beijing health app to record Covid-19 risk, testing and vaccination status had suffered cyberattacks from overseas on Thursday, a government spokeswoman said. She said such attacks on the Health Kit app also occurred during the Winter Olympics but were handled effectively. Local infections in Beijing spiked slightly on Thursday morning with 50 positive cases bringing the total in this outbreak to 164. About 30 per cent of those infected were students, prompting several districts to suspend in-person classes. Li Yi, spokesman for the city’s Education Commission, said all kindergartens, primary and middle schools will start May Day holidays a day earlier on Friday, so they can participate in the mass testing and “cut the risk of epidemic transmission and acceleration” to the minimum. Classes are due to resume next Tuesday, but the actual time of reopening would depend on the pandemic situation, Li said. In Tongzhou district – home to the city’s administrative offices – all schools from kindergarten upwards had switched to online learning after a teacher and three students tested positive. Several other districts, including Xicheng and Chaoyang, also ordered schools to close and move classes online on Wednesday night. Chaoyang, Beijing’s biggest district, reported the first cases in the current outbreak and has logged the highest concentration of positives so far. The district added more temporary “control areas” on Thursday morning. Those living in control areas must not leave their residential estates, while shops, restaurants, entertainment venues and stadiums there are closed. Chinese authorities vow to crack down on Covid price gougers Office buildings in Chaoyang are also demanding extra proof of Covid-negative status before granting entry. In addition to a green health code – indicating no travel to at-risk areas in the past two weeks – people must provide a negative nucleic acid test result from the previous 48 hours. One notice to tenants in Chaoyang’s central business district said: “According to requirements of epidemic control in the district, all people entering the building need to produce those two reports … please take with you office equipment such as computers for emergencies.” Temporary control areas were also declared in two villages in Guangzhou’s Huadu district, where the affected airport is located. Residents are banned from leaving their homes and schools have switched to online learning. Social venues have been ordered to close, at least until the end of Friday.