Construction crews from mainland China were helping Hong Kong build two temporary isolation facilities to house thousands of coronavirus patients as a senior official declared the city “in full combat mode”.

The crowded Chinese financial hub is in the throes of its worst-ever coronavirus outbreak, registering thousands of confirmed cases a day as hospitals reach breaking point.

A strict zero-Covid policy like China uses kept infections at bay for two years but left the city cut off internationally, AFP reports.

And when the highly transmissible Omicron variant broke through, authorities were caught flat-footed with a dangerously under-vaccinated elderly population and few plans in place to deal with a mass outbreak.