China placed all 17 million residents in one of its biggest cities under lockdown on Sunday, as virus cases doubled nationwide to nearly 3,400 and anxiety mounted over the resilience of its 'zero-Covid' approach in the face of the worst outbreak in two years.

The southern tech hub of Shenzhen told all residents to stay at home as the city struggles to eradicate an Omicron flare-up linked to neighbouring virus-ravaged Hong Kong. ...

The surge in infections across China has also prompted authorities to close schools in Shanghai and lock down multiple northeastern cities, as 18 provinces battle clusters of the Omicron and Delta variants. ...