The Chinese city of Qingdao is to test its entire population of nine million people for Covid-19 in just five days.
The mass testing comes after a dozen new cases were linked to a hospital treating coronavirus patients who have returned from overseas.
The city reported six new coronavirus cases and six asymptomatic cases all said to be linked to Qingdao Chest Hospital.
Qingdao has locked down the hospital as well as the emergency department of its central hospital.
Buildings that the infected individuals live in have also been locked down as part of containment measures.
Daily Covid infections in mainland China have fallen drastically from peaks early this year, but the country remains on high alert in order to prevent lockdowns that saw a sharp decline in the world's second biggest economy.
The total number of confirmed cases in mainland China now stands at 85,578, while the death toll remains at 4,634.
The last reported virus transmissions within the country were four patients found on August 15 in the northwestern city of Urumqi in the far western Xinjiang region.
All the cases reported since then were in travellers from outside the mainland.
Additional reporting by agencies
