New Delhi, Jan 5 (IANS): China has put a second city under total lockdown after just three asymptomatic Covid cases were discovered from there, the BBC reported.

Yuzhou, which has a population of 1.1 million, saw its transport system shut down and all but essential food stores closed overnight, the report said.

It follows a similar lockdown in Xi'an, where 13 million have been confined to their homes since December 23.

The strict measures come ahead of the Lunar New Year and the Winter Olympics due to be held in Beijing from February 4-20.

With exactly a month to go until the Games start, Foreign Ministry spokesman Wang Wenbin assured reporters that China has "formulated an efficient and highly effective defence system".

As part of this system, thousands of staff and volunteers started entering a bubble on Tuesday, which will see them have no physical contact with the outside world in order to limit the spread of the virus.

Participants and international media arriving to cover the Games will also enter the bubble on arrival in China, where they will remain for the duration of their stay, the report said.

In Yuzhou, some 700 km south-west of Beijing, officials said that "to curb and quash the epidemic within the shortest amount of time is a high-priority political task" for both citizens and government employees.

All residents have been told to remain indoors, with only those involved in containing the disease allowed to move.