The Chinese metropolis of Chengdu has announced a lockdown following the spread of the coronavirus. It is the first such move by a large Chinese city in about three months.

Officials in the city in Sichuan Province say they counted more than 700 cases of coronavirus infections between August 25 and 31. Chengdu has a population of about 21 million.

The officials initiated a four-day lockdown across the city from Thursday night, citing fears that the virus may spread further. They are urging residents to take PCR tests during the period.

This is the first lockdown of a Chinese metropolis since a similar measure was put in place across Shanghai for more than two months from late March.

The virus spread in Chinese resorts, including the southern island of Hainan, in August. Infections have also been resurging in cities, such as Guangzhou and Shenzhen in the south and Dalian in the northeast, after the end of the summer holiday period.

Authorities in those areas have restricted outings, disrupting people's lives. The measure has also hurt consumption, slowing China's economic recovery.