People in China who attended weekend protests against Covid restrictions say they have been contacted by police, as authorities begin clamping down.
Several people in Beijing said police had called demanding information about their whereabouts.
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.
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.