Prime Minister Boris Johnson has been admitted to hospital for tests, 10 days after testing positive for coronavirus, Downing Street has said.
He was taken to a London hospital on Sunday evening with "persistent symptoms" - including a temperature.
It is said to be a "precautionary step" taken on the advice of his doctor.
The prime minister remains in charge of the government, but the foreign secretary is expected to chair a coronavirus meeting on Monday morning.
Mr Johnson, 55, spent the night in hospital and is having what has been described as a series of "routine tests".
In a statement, a Downing Street spokeswoman said: "On the advice of his doctor, the prime minister has tonight been admitted to hospital for tests.
"This is a precautionary step, as the prime minister continues to have persistent symptoms of coronavirus 10 days after testing positive for the virus."
She added: "The prime minister thanks NHS staff for all of their incredible hard work and urges the public to continue to follow the government's advice to stay at home, protect the NHS and save lives."
US President Donald Trump began a White House press briefing by sending "our nation's well wishes" for Mr Johnson's "own personal fight with the virus".
"All Americans are praying for him. He's a great friend of mine, a great gentleman and a great leader," Mr Trump said, adding that he was sure the prime minister would be fine because he is "a strong person".
Labour leader Keir Starmer also wished Mr Johnson well, saying he hoped for a "speedy recovery".
PUKmedia / BBC