People in China who attended weekend protests against Covid restrictions say they have been contacted by police, as authorities begin clamping down, according to a media report.
Several people in Beijing said police had called demanding information about their whereabouts, BBC reported.
It is unclear how police might have discovered their identities.
On Tuesday, officials renewed a promise to speed up efforts to vaccinate older people. Vaccination rates among elderly people are relatively low.
China has recorded record numbers of new cases in recent days.
Over the weekend, thousands in China took to the streets demanding an end to Covid lockdowns - with some even making rare calls for President Xi Jinping to stand down, BBC reported.
But on Monday, planned protests in Beijing did not happen after officers surrounded the assembly point. In Shanghai, large barriers were erected along the main protest route and police made several arrests.
The demonstrations began after a fire in a high-rise block in Urumqi, western China, killed 10 people on Thursday. Many Chinese believe Covid restrictions contributed to the deaths, although the authorities deny this.
Asked whether the protests would prompt a change to zero-Covid rules, an official said China would continue to "fine tune and modify" its measures.
"We are going to maintain and control the negative impact to people's livelihoods and lives," said Mi Feng, a National Health Commission spokesman, at a press conference.
On Tuesday morning, police could be seen in both Beijing and Shanghai patrolling areas where some groups on the Telegram messaging app had suggested people should gather again, BBC reported.
A small protest in the southern city of Hangzhou on Monday night was also quickly stopped with people swiftly arrested.
Reports also say that police were stopping people and searching their phones to check if they had virtual private networks (VPNs) set up, as well as apps such as Telegram and Twitter which are blocked in China, BBC reported.
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