China has placed all 17 million residents in one of its biggest cities under lockdown.

The tech city of Shenzhen reported 66 cases on Sunday, while China recorded 3,400, in its worst outbreak in two years.

It’s led to increased anxiety over the nation’s ‘zero-Covid’ approach.

The cases are linked to neighbouring virus-ravaged Hong Kong, which recorded over 32-thousand on the same day.

The lockdown last until March 20, and the city is planning to launch three rounds of mass testing.

The move extends an earlier lockdown imposed on the city’s central business district.

Officials have largely resisted tactics such as lockdowns and mass testing and relied mostly on targeted responses, only to see Omicron continue to spread.

Shenzhen is also under pressure to prevent infections from seeping in through Hong Kong, which has seen daily cases rise to tens of thousands.

The operations of nine cross-province bus stations that mainly offered service to provinces including Jiangsu, Zhejiang, Anhui, Shandong and Jiangxi were halted.

Shanghai will suspend all cross-province bus services from March 14.