British Prime Minister Boris Johnson has been taken into intensive care in hospital after his COVID-19 worsened, his office said on Monday.

"Since Sunday evening, the Prime Minister has been under the care of doctors at St Thomas' Hospital, in London, after being admitted with persistent symptoms of coronavirus," Downing Street said.

"Over the course of this afternoon, the condition of the Prime Minister has worsened and, on the advice of his medical team, he has been moved to the Intensive Care Unit at the hospital.