The Prime Minister was admitted to hospital on Sunday after his coronavirus symptoms worsened. And on Monday evening Mr Johnson was moved to intensive care after his symptoms took another turn for the worse.
Russian media took the opportunity to suggest Mr Johnson will soon be placed on a ventilator to aid his breathing.
Publication RIA-Novosti reported the unverified news, attributing its source to someone “close to the leadership” of the NHS.
Speaking before the Prime Minister went into intensive care, his spokesperson said: "That is disinformation.
“Our specialist government units have seen a rise in false and misleading narratives since the coronavirus pandemic started.
"It's vital that any disinformation is knocked down quickly."
No 10 slammed Russia for "disinformation" surrounding Boris Johnson's hospital admission
Russian media RIA-Novosti claimed to have been told the news by a source close to NHS leadership
He also revealed that the government was working with social media companies to "press for further action to stem the further spread of falsehood and rumours".
Downing Street said Mr Johnson remains conscious and was moved to intensive care as a precaution should he require ventilation in the coming days.
Mr Johnson is said to be receiving “excellent care” in an NHS hospital in London.
Dominic Raab has currently assumed a leading role in leading the government against coronavirus
Foreign Secretary Dominic Raab has taken on the role of First Secretary of State and Secretary of State and has been asked by Mr Johnson to deputise "where necessary”.
The Queen has been kept informed about the prime minister’s health by No 10, according to Buckingham Palace.
Mr Johnson was given oxygen late on Monday afternoon before being taken into intensive care, according to the BBC’s Chris Mason.
A Number 10 statement read: "The prime minister has been under the care of doctors at St Thomas' Hospital, in London, after being admitted with persistent symptoms of coronavirus.
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Last month Boris Johnson announced he has tested positive for coronavirus
Donald Trump has said he has sent help to Johnson after hearing the news
"Over the course of (Monday) 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."
Meanwhile, the government has continued to work through its plans and implement measures to restrict the virus’ spread.
Mr Raab said there was an "incredibly strong team spirit" behind the Prime Minister.
The current live coronavirus map of the UK
He added that he and his colleagues were making sure they implemented plans Mr Johnson had instructed them to deliver "as soon as possible".
He said: "That's the way we'll bring the whole country through the coronavirus challenge.”
There are currently 51, 608 confirmed cases of the coronavirus in the UK.
More than 5,000 people have died.
The Queen is being updated on the PM's condition by No 10
Worldwide, 1.3million people have been infected with the virus while over 70,000 have died.
There are seven makeshift hospitals across the UK known as Nightingale hospitals.
The newest addition will be established at the Principality Stadium in Cardiff, though will not be classed as Nightingale hospital.