Authorities in China have locked down Chengdu, a southwestern city of 21 million people, following a spike in COVID-19 cases.

According to reports, residents have been ordered to stay home, and at least 70% of the flights have been suspended to and from the city, which is a major transit hub in Sichuan province and a governmental and economic centre.

The start of the new school term has also been delayed, although public transport continues to operate and citizens are permitted to leave the city if they can show a special need.

Authorities also announced that just one member of each family who can show a negative virus test within the past 24 hours is allowed out per day to buy necessities.

There has been no word as to when the lockdown would be lifted.