Authorities in the Chinese city of Shanghai are tightening information control after daily coronavirus cases hit another high despite a citywide lockdown.

The authorities warned on Friday that those who illegally spread false information will face consequences.

The warning came after the city confirmed 21,222 new infections on Thursday. The tally is the first over 20,000 and the seventh straight record high.

Officials are carrying out PCR and antigen tests on residents throughout the city. They say they will decide how to respond to the situation based on test results, but have not indicated when restrictions will be lifted.

Social media are rife with rumors and other unverified information.

On March 23, Shanghai police announced that they were investigating two men on suspicion of disturbing public order by posting on social media that a lockdown would soon be introduced.

Authorities were negative about a citywide lockdown at the time, but eventually introduced the measure.

Some people took to the internet to raise questions about the credibility of official announcements and criticize information restrictions.