London (AFP) - British Prime Minister Boris Johnson said his personal battle with the coronavirus "could have gone either way" and said there was "no question" doctors saved his life, speaking in a candid video message after leaving hospital Sunday.

The UK leader checked into hospital a week ago and spent three days in intensive care after he was diagnosed with COVID-19 at the end of March, the most high-profile leader to come down with the virus.

Dressed in a suit and tie, Johnson thanked his doctors and vowed to help Britain defeat the virus as the country's death toll topped 10,000 Sunday -- a grim milestone only a handful of countries have passed.

"I hope they won't mind if I mention in particular two nurses who stood by my bedside for 48 hours when things could have gone either way," said Johnson, referring to the state-run National Health Service (NHS) staff who cared for him at London's St Thomas' Hospital.

He said he was discharged after "a week in which the NHS has saved my life, no question", and officials said he would now convalesce at Chequers, the country estate of British prime ministers, on the advice of his medical team.

"The reason in the end my body did start to get enough oxygen was because for every second of the night they were watching and they were thinking and they were caring and making the interventions I needed," he said of the medical staff.

He added that Britain "will defeat this coronavirus and defeat it together" as he implored citizens to maintain a nationwide lockdown imposed three weeks ago.

But the country is now seeing daily death tolls to match those previously seen in Europe's hardest-hit nations Italy and Spain, after recording nearly 1,000 fatalities on Friday and Saturday. There were 737 new deaths reported Sunday.

With 10,612 fatalities, Britain now has the world's fifth highest death toll -- behind the US, Italy, Spain and France -- but the actual figure may be higher as the count does not include those who have died in care centres or at home.

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"Today marks a sombre day in the impact of this disease as we join the list of countries who have seen more than 10,000 deaths related to coronavirus," Britain's Health Minister Matt Hancock said.

Britain's tally of confirmed cases has climbed to over 84,000, thought to be only a fraction of the true number of infections as testing has been limited.

- 'Dark times' -

It is unclear how quickly Johnson will be able to return to work, with Foreign Secretary Dominic Raab currently deputising for him.

Johnson's pregnant fiancee Carrie Symonds, who also suffered from coronavirus symptoms in recent weeks, also thanked his "magnificent" health staff.

"I will never, ever be able to repay you and I will never stop thanking you," she said on Twitter, adding she felt "incredibly lucky".

"There were times last week that were very dark indeed. My heart goes out to all those in similar situations, worried sick about their loved ones."

His father Stanley Johnson also praised the medical team.

"I realise now -- I think the whole country realises -- how close he came to a crisis situation," he said.

It remains uncertain when Britain might be able to lift stringent social distancing measures rolled out on March 23.

The lockdown order is set for a formal review next week and is likely to remain in place until at least the end of the month.

Queen Elizabeth II urged Britons to keep staying home, in what is believed to be her first pre-recorded Easter address, released by Buckingham Palace on Saturday evening.

"By keeping apart we keep others safe," the 93-year-old monarch said. "We know that coronavirus will not overcome us."

Her resolute comments came a week after a rare televised address to the nation in which she told people to unite to beat COVID-19.

Meanwhile, the government has been forced to defend its patchy rollout of personal protective equipment (PPE) for medical staff.

"We are making sure we get the equipment to the front line," senior minister Alok Sharma said on Sunday, noting a "squeeze on supply" amid a "huge global demand for PPE".

So far 19 NHS staff have died from COVID-19, Hancock said this weekend, but added that a lack of PPE was not to blame.

A senior doctor pleaded on social media last month with Johnson for better protection against the disease. The doctor since died.