At least one person has died in the United Kingdom after contracting the Omicron coronavirus variant, the country's Prime Minister Boris Johnson said on Monday, the first publicly confirmed death globally from the spreading strain.

Britain gave no details on the death other than the person had been diagnosed in hospital. It was not clear if the patient had been vaccinated or had underlying health issues.

Deaths from Omicron may have occurred in other countries but none has been publicly confirmed yet outside Britain.

The World Health Organization said on Sunday that while preliminary findings from South Africa suggest Omicron may be less severe than the Delta variant – currently dominant worldwide, and all cases reported in the Europe region have been mild or asymptomatic, it remains unclear to what extent Omicron may be inherently less virulent.