Hundreds of demonstrators and police clashed in Shanghai on Sunday night as protests over China's stringent COVID-19 restrictions flared for a third day, spreading to several cities in the wake of a deadly apartment fire in the country's far west. The wave of civil disobedience is unprecedented in mainland China since President Xi Jinping assumed power a decade ago, as frustration mounts over his signature zero-COVID policy nearly three years into the pandemic. The COVID-19 measures are also exacting a heavy toll on the world's second-largest economy. A fire on Thursday at a residential highrise building in the city of…