Boris Johnson is able to walk again after he was moved back from intensive care to a hospital ward, Downing Street says.
Mr Johnson waved his thanks to NHS doctors and nurses as he left the intensive care unit, his spokesman confirmed on Friday.
But they said it was too early to say how long he would need to stay in hospital.
"Decisions such as this will be on the advice of his medical team. They have given him brilliant care," the spokesman added.
A statement from Number 10 said: "The prime minister has been able to do short walks, between periods of rest, as part of the care he is receiving to aid his recovery.
"He has spoken to his doctors and thanks the whole clinical team for the incredible care he has received.
"His thoughts are with those affected by this terrible disease."
He was taken to St Thomas' hospital in central London on Sunday night - ten days after testing positive for COVID
Fears grew for his health when his symptoms worsened and he was transferred to intensive care the following day.
He spent three nights there before Downing Street confirmed he was in the "early phase of his recovery" and moved back to a normal hospital ward.
Earlier, it was confirmed the daily number of UK coronavirus deaths was 980 - surpassing Spain and Italy's highest daily totals.
The death toll in UK hospitals is now 8,958.
Foreign Secretary Dominic Raab is deputising for the prime minister in his absence.
Addressing the government's daily coronavirus news conference on Thursday, Mr Raab said it was too early to consider lifting the UK's lockdown.
A huge publicity blitz is urging the public to stay at home, not visit friends or family and observe the rules over the Easter weekend.
And with temperatures set to soar, police forces have warned they are ready to take action against those who flout rules designed to slow the spread of COVID
However, concerns remain over how some police are enforcing the rules.
Cambridgeshire Police had to clarify its social distancing guidelines after an officer posted on social media they were monitoring "non-essential" supermarket aisles.
An officer in Doncaster was also filmed telling a man to stay out of his front garden and go inside.