The World Health Organisation met Chinese officials for talks on Friday about the surge in Covid-19 cases, urging them to share real-time data so other countries can respond effectively.
The rise in infections in China has triggered concern around the globe and questions about its data reporting, with low official figures on cases and deaths despite some hospitals and morgues being overwhelmed.
The talks came after WHO chief Tedros Adhanom Ghebreyesus urged Beijing to be more forthcoming on the pandemic situation in the world's most populous country.
The UN health agency said the meeting was "to seek further information on the situation, and to offer WHO's expertise and further support."
It said officials from China's National Health Commission and the National Disease Control and Prevention Administration briefed the WHO on China's evolving strategy and actions on epidemiology, variant monitoring, vaccination, clinical care, communication and research and development.
"WHO again asked for regular sharing of specific and real-time data on the epidemiological situation -- including more genetic sequencing data, data on disease impact including hospitalisations, intensive care unit admissions and deaths," it said.
It asked for data on vaccinations delivered and vaccination status, especially in vulnerable people and those aged over 60.
"WHO reiterated the importance of vaccination and boosters to protect against severe disease and death for people at higher risk," the Geneva-based organisation said.
"WHO called on China to strengthen viral sequencing, clinical management, and impact assessment, and expressed willingness to provide support on these areas, as well as on risk communications on vaccination to counter hesitancy."
The UN agency said Chinese scientists were invited to engage more closely in WHO-led Covid-19 expert networks, and asked them to present detailed data at a virus evolution advisory group meeting on Tuesday.
"WHO stressed the importance of monitoring and the timely publication of data to help China and the global community to formulate accurate risk assessments and to inform effective responses," it said.
China said this month it would end mandatory quarantine for people arriving in the country and that it had abandoned strict measures to contain the virus.
The surge in cases in China comes almost exactly three years on since the first infections were recorded in the Chinese city of Wuhan in late 2019.
Since then, more than 650 million confirmed Covid cases and over 6.6 million deaths have been reported, though the UN health agency acknowledges this will be a vast undercount.
The search for the origins of the virus remains unresolved, with Tedros insisting all hypotheses remain in the table, including the theory that the virus escaped from Wuhan's virology laboratories.
Tedros has called on China to share data and conduct the studies requested by the WHO to better understand where the SARS-CoV-2 virus that causes Covid-19 disease sprang from.