Shanghai reported over 13,000 new local infections Tuesday, more than tripling the number reported nine days ago, when it said it would close down half of the city at a time for four days. The part of the city locked down in the first phase had been scheduled to emerge Friday. The second stage was due to end at 3 a.m. Tuesday.

Late Monday, city authorities said the lockdown would continue while the situation is evaluated and the result of citywide Covid-19 testing is analyzed…

Managing a potentially weekslong lockdown of 25 million people is unprecedented even in China, where local authorities have adhered to a strategy of trying to stamp out outbreaks quickly wherever they occur.