The British prime minister, already in hospital for tests, was taken to intensive care after his condition worsenedt.
UK Prime Minister Boris Johnson, in hospital since Sunday with coronavirus, has spent the night in an intensive care unit after his condition worsened on Monday evening.
"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 in a statement on Monday evening.
"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."
The Downing Street statement added that Boris Johnson has asked Foreign Secretary Dominic Raab, who is the First Secretary of State, "to deputise for him when necessary".
"The PM is receiving excellent care, and thanks all NHS staff for their hard work and dedication," the statement read.
Boris Johnson was moved to the intensive care unit at St Thomas’ Hospital around 19:00 GMT, Downing Street said, after his condition worsened over the course of Monday afternoon.
The decision was made by the PM’s medical team.
The PM remains conscious at this time, Downing Street added: "He has been moved to the ICU as a precaution should he require ventilation to aid his recovery."
Boris Johnson was hospitalised on Sunday evening for "routine tests" as he was still experiencing coronavirus symptoms, he said. He had been self-isolating for a week after feeling the first symptoms and testing positive for COVID-19.
"I am in good spirits and keeping in touch with my team", Boris Johnson said on social media.
British politicians and world leaders have sent support and wishes of quick recovery to Johnson.
David Cameron, Johnson's old university friend and his predecessor as British Prime minister, said: "Get well soon. (...) We all want you safe, well and back in Downing Street."
France's Emmanuel Macron has addressed his support "to Boris Johnson, his family and the British people in this difficult time".