A district of Beijing was on a "wartime" footing and the capital banned tourism on Saturday after a cluster of novel coronavirus infections centred around a major wholesale market sparked fears of a new wave of COVID-19.

Concern is growing of a second wave of the pandemic, which has infected more than 7.66 million people worldwide and killed more than 420,000, even in many countries that seemed to have curbed its spread.

Chu Junwei, an official of Beijing's southwestern Fengtai district, told a briefing on Saturday that the district was in "wartime emergency mode."