British Prime Minister Boris Johnson was admitted to hospital for tests on Sunday in what Downing Street said was a "precautionary step" because he was showing persistent symptoms of coronavirus 10 days after testing positive for the virus.

Johnson, who was isolating in Downing Street after testing positive last month, still had a high temperature and so his doctors felt he should go to hospital for tests. He remains in charge of the British government, his Downing Street office said.

"On the advice of his doctor, the prime minister has tonight been admitted to hospital for tests," Downing Street said.

"This is a precautionary step, as the prime minister continues to have persistent symptoms of coronavirus 10 days after testing positive for the virus."

News of his hospitalization came only an hour after Queen Elizabeth delivered a rallying call to the British public saying they would overcome the coronavirus outbreak if they stayed resolute.

Johnson, 55, on March 27 became the first leader of a major power to announce that he had tested positive. He went into isolation at an apartment in Downing Street and said on Friday he was staying there as he still had a high temperature.

"Although I'm feeling better and I've done my seven days of isolation, alas I still have one of the symptoms, a minor symptom, I still have a temperature," a weary-looking Johnson, sitting in a chair with his shirt open at the neck, said in a Twitter video message on Friday.

Downing Street underscored that this was not an emergency admission and that Johnson remains in charge of the government.

"Wishing the prime minister well and a speedy recovery," Keir Starmer, the newly elected leader of the opposition Labour Party, said.

Johnson's response to pandemic initially criticized

Johnson has faced criticism in the United Kingdom for initially approving a much more modest response to the novel coronavirus outbreak than other major European leaders.

But he swiftly changed tack when projections showed a quarter of a million people could die in the U.K.

He effectively shuttered the world's fifth-largest economy, advising people to stay at home and the elderly or infirm to isolate themselves for weeks.

But the virus penetrated the British government. Johnson and his health minister tested positive last month and his chief medical adviser also self isolated.

In this March 9 file photo, Britain's Prime Minister Boris Johnson and his partner Carrie Symonds arrive to attend the annual Commonwealth Day service at Westminster Abbey in London. Johnson was diagnosed with coronavirus 10 days ago. Symonds, Johnson's 32-year-old pregnant fiancée, said on Saturday that she had spent the past week in bed with symptoms of the coronavirus but is on the mend. (Kirsty Wigglesworth/The Associated Press)

Carrie Symonds, Johnson's 32-year-old pregnant fiancée, said on Saturday that she had spent the past week in bed with symptoms of the novel coronavirus but after seven days of rest felt stronger and was on the mend.

"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," Downing Street said.

The United Kingdom's death toll from the coronavirus rose by 621 to 4,934 the health ministry said on Sunday. A total of 195,524 people had been tested of which 47,806 tested positive.