The head of the World Health Organization (WHO) on Wednesday said he was "very concerned" about an unprecedented wave of Covid cases in China, as the health body urged Beijing to accelerate vaccination of the most vulnerable.

"WHO is very concerned over the evolving situation in China, with increasing reports of severe disease," Tedros Adhanom Ghebreyesus told a weekly news conference, appealing for detailed information on disease severity, hospital admissions and intensive care requirements.