Mushrooming outbreaks of the highly contagious Delta variant prompted China and Australia to impose stricter Covid-19 restrictions on Saturday as the WHO urged the world to quickly contain the mutation before it turns into something deadlier and draws out the pandemic.

Axar.az reports citing foreign media that China's most serious surge of coronavirus infections in months spread to two more areas Saturday - Fujian province and the sprawling megacity of Chongqing.

More than 200 cases have been linked to a Delta cluster in Nanjing city where nine cleaners at an international airport tested positive, with the outbreak spanning Beijing, Chongqing and five provinces as of Saturday.

The nation where the disease first emerged has rushed to prevent the highly transmissible strain from taking root by putting more than one million people under lockdown and reinstituting mass testing campaigns.