The United States has warned Americans thinking of travelling to China that they may be subject to "arbitrary" local law enforcement and coronavirus restrictions.
"Do not travel to the PRC [People's Republic of China]'s Hong Kong special administrative region, Jilin province and Shanghai municipality due to Covid-19-related restrictions, including the risk of parents and children being separated," the travel alert released by the US Department of State on Friday said.
"Reconsider travel to the PRC's Hong Kong [Special Administrative Region] due to arbitrary enforcement of local laws."
Do you have questions about the biggest topics and trends from around the world? Get the answers with SCMP Knowledge, our new platform of curated content with explainers, FAQs, analyses and infographics brought to you by our award-winning team.
It also said China's zero-tolerance approach would severely hit travel and access to public services, while all travellers should prepare to quarantine at a government-designated location for a minimum of 14 days upon arrival.
The US Centres for Disease Control and Prevention also issued a level one travel health notice for China, meaning caution for disease outbreaks or crises that disrupt a country's medical infrastructure.
The travel alert, the third highest of the four-tier system, came as the highly contagious Omicron variant has spread to much of China, including big cities with large expat communities such as Shanghai and Beijing.
While many Western countries, which treat Omicron as a stronger sort of flu, have chosen to live with the virus, Beijing insists on dynamic clearing at all costs.
Shanghai, lying in the eye of the current pandemic storm, has been put under de facto lockdown for more than a week. The city reported 22,609 new asymptomatic cases and 1,015 symptomatic ones on Saturday, in a new daily high.
This has prompted complaints of food shortages and viral videos of disgruntled residents scuffling with officials.
The US has allowed non-essential government employees and their family members to leave Shanghai during the outbreak.
A spokesman for the embassy in Beijing confirmed that the consular section in Shanghai was closed to the public because of local Covid-19 control measures and it would reopen as soon as permitted.
"Ambassador [Nicholas] Burns and other department and mission officials have raised our concerns regarding the outbreak and the PRC's control measures directly with PRC officials, and we have informed them about the voluntary departure decision," the spokesman said.