Chinese authorities have begun inquiries into some of the people who gathered at weekend protests against COVID-19 curbs, three people who were at the Beijing demonstrations told Reuters, as police remained out in numbers on the city's streets.
In one case, a caller identifying as a police officer in the Chinese capital asked the protester to show up at a police station on Tuesday to deliver a written record of their activities on Sunday night.
In another, a student was contacted by their college and asked if they had been in the area where events took place and to provide a written account.
"We are all desperately deleting our chat history," one Beijing protester who declined to be identified, told Reuters.
"There are just too many police. Police came to check the ID of one of my friends and then took her away. We don't know why. A few hours later they released her."
Beijing's Public Security Bureau did not immediately respond to a request for comment.
Simmering discontent with stringent COVID prevention policies three years into the pandemic ignited into broader protests in cities thousands of miles apart over the weekend.
Mainland China's biggest wave of civil disobedience since President Xi Jinping took power a decade ago comes as the number of COVID cases hit record daily highs and large parts of several cities face new lockdowns.
COVID in China keeps spreading despite the efforts of most of its 1.4 billion people to prevent transmission by adhering to a zero-COVID policy of eradicating all outbreaks and maintaining tight border controls.
The lockdowns have exacerbated one of the sharpest slowdowns in growth China has suffered in decades, disrupting global supply chains and roiling financial markets.
On Tuesday, Asian shares rallied as unsubstantiated rumours swirled that the unrest might prompt an earlier loosening of the COVID restrictions. Similar rumours have caused markets to zig-zag in recent weeks.
In Hangzhou, the capital of the eastern province of Zhejiang, videos on social media which Reuters could not independently verify showed hundreds of police occupying a large square on Monday night, preventing people from congregating.
One video showed police, surrounded by a small crowd of people holding smartphones, making an arrest while others tried to pull back the person being detained.
Hangzhou police did not immediately comment.
In Shanghai and Beijing, police were patrolling areas where some groups on the Telegram messaging service had suggested people gather again. The police presence on Monday night ensured no gatherings took place.
"It's really scary," said Beijing resident Philip Qin, 22, of the large numbers of police officers on the streets.
Residents said police have been asking people passing through those areas for their phones to check if they had virtual private networks (VPNs) and the Telegram app, which has been used by protesters, residents said. VPNs are illegal for most people in China, while the Telegram app is blocked from China's internet.
A busload of demonstrators was taken away by police during Sunday night protests in Shanghai.
The catalyst for the protests was a fire last week in the western city of Urumqi that authorities said killed 10 people.
Some internet users said COVID lockdown measures hampered the effort to rescue people in the burning building. Officials have denied that.
Students from several colleges in the Sichuan province who took part in campus memorials for the victims have been asked by their teachers who the main organiser was, said a person who attended one in Chengdu, the province's capital.
Prominent nationalist bloggers with millions of followers, such as Ren Yi, the grandson of Communist Party leader Ren Zhongyi, and Yu Li, who uses the pen name of Sima Nan, wrote this week that the protests were fomented by "foreign forces".
"What is their purpose? On one hand, it is to intensify internal conflicts. On the other hand, it is to see if they can completely politicize the issues around our epidemic prevention and health policies," Ren wrote in his "Chairman Rabbit" blog.
Chinese authorities regularly warn that "foreign forces" are endangering national security and have accused them of stirring the 2019 pro-democracy Hong Kong protests.
"Blaming it on foreign forces is a standard tactic," said Alfred Wu, associate professor at the Lee Kuan Yew School of Public Policy. "This is how the party shirks responsibility and rallies people behind it."
Officials say China's COVID policies have kept the death toll in the thousands, avoiding the millions of deaths elsewhere.
Many analysts say easing the policy could lead to widespread illness and deaths, overwhelming hospitals. A strong push on vaccinating the elderly is required before China could even contemplate re-opening, they say.
In a Tuesday editorial that did not mention the protests, People's Daily, the Party's official newspaper, urged citizens to "unswervingly implement" COVID policies, saying victory comes with "perseverance through thousands of hardships".
"The harder it is, the more you have to grit your teeth," it said.