Large-scale COVID-19 testing was ordered in Zhongshan City, south China's Guangdong Province on Thursday after the city reported one asymptomatic case related to Nanjing where a new cluster of infections is emerging. 

People are asked to not leave the city for unnecessary travel and to take proper health protection. 

Starting Friday, people leaving the city must provide a local "green code" for COVID-19 and negative test result of nucleic acid testing taken within 48 hours before departure.