The National Health Commission has reported the highest number of daily Covid-19 cases since the start of the pandemic nearly three years ago.

Excluding imported cases, the number of new local cases was 31,444 on Wednesday, up from 28,883 the day before.

The previous record for daily infections was set on April 13, when local coronavirus cases hit 29,317.

One more death was also confirmed – from Beijing – pushing fatalities on the mainland up to 5,232.

As of November 23, the mainland had reported 297,516 Covid cases with symptoms.

Infections in Beijing continued to grow. The capital reported 1,648 new locally transmitted cases for Wednesday, compared with 1,486 a day earlier.

Health authorities in Shanghai reported 67 cases, down one from Tuesday.

New infections in Guangzhou subsided further. The city of nearly 19 million people had 7,620 cases on Wednesday, compared with 9.970 a day before, according to local authorities.

But Covid cases in the mainland's largest municipality, Chongqing, climbed to 7,846, from 6,943 on Tuesday.

The central city of Zhengzhou, which is home to a massive iPhone factory, is reported to have ordered an effective lockdown for several districts, as officials struggle to control an outbreak that has sparked protests and panic.

The local government is said to have told residents of the city's centre that they can't leave the area unless they have a negative Covid test and permission from local authorities, and are advised not to leave their homes "unless necessary".

Apple said on Thursday it has team members on the ground at the Foxconn iPhone manufacturing facility.

"We have Apple team members on the ground at our supplier Foxconn’s Zhengzhou facility. We are reviewing the situation and working closely with Foxconn to ensure their employees' concerns are addressed," the company said.

Foxconn, for its part, acknowledged a "technical error" when hiring new recruits at the factory and apologised to workers.

Workers said they had been informed that Foxconn intended to delay bonus payments. Some also complained they were forced to share dormitories with colleagues who had tested positive for Covid.

"Our team has been looking into the matter and discovered a technical error occurred during the onboarding process," Foxconn said in a statement, referring to the hiring of new workers.

"We apologise for an input error in the computer system and guarantee that the actual pay is the same as agreed and the official recruitment posters."

The largest protests had reportedly died down by Thursday.

The Zhengzhou plant employs more than 200,000 people to make Apple devices. (Agencies)