A five-year-old child with underlying health conditions is among those with coronavirus whose deaths were reported in the past day, Cabinet Office Minister Michael Gove has said.
The latest figures show 4,313 people with the virus have now died in the UK - up by 708 on Friday's figure.
Mr Gove said hundreds of ventilators were being manufactured every day and more had been sourced from abroad.
People have been warned to stay at home despite the warm weather this weekend.
Speaking alongside Mr Gove at the government's daily briefing, NHS England medical director Stephen Powis said: "The sun might be out, but that does not mean you should be out."
He said there was some evidence that social distancing measures were reducing transmission, and that the latest figures suggested new cases had begun to "stabilise".
However, he stressed that there was "no room for complacency".
During the briefing, Mr Gove paid tribute to one of the youngest victims of the outbreak.
"Our thoughts today are also with the family of the five-year-old with underlying health conditions who has tragically died," he said.
By Robert Cuffe, BBC News Head of Statistics
The recent trends in deaths (doubling roughly every 3.5 days) would have predicted about 800 deaths today.
Remember that doubling every few days means that we should expect to see record new highs regularly.
Scientists remind us to look for evidence that the growth is slowing down - the first step on the journey to falling numbers of deaths.
So, compared to that projection, there is a potential silver lining to these figures - if the pattern continues.
But one day of below-trend growth is far too soon to know for sure.
It takes over three weeks from infection to death to being reported in these figures.
So while we can hope to see the effects of pre-lockdown social distancing soon, it will take longer for the effect of the lockdown, announced on 23 March, to become apparent.
There are now 41,903 confirmed cases in the UK, the Department of Health said.
There were 212 deaths in the Midlands, more than in London, where there were 127.
Mr Gove said seven healthcare professionals have now died.
Urging people to stay at home, he called on the public to remember two NHS nurses who died on Friday after contracting Covid-19.
He said: "Each had three young children. They died doing everything they could to help the sick and suffering."
Meanwhile, Prime Minister Boris Johnson remains in self-isolation in Downing Street after testing positive for coronavirus while his pregnant partner Carrie Symonds tweeted that she has spent a week in bed with the main symptoms.
She said she had not been tested for the virus.
Prof Powis said people were adhering to social distancing measures, and that public transport use remains "extremely low".
School attendance was down as low as 2%, Mr Gove added.
However, Prof Powis added that people must "resist the temptation" to go out in the warm weather.
Brighton and Hove City Council tweeted on Saturday that too many people were meeting up with friends on the seafront, making social distancing "impossible".
Sussex Police said that two people had been summonsed to attend court after having a barbecue on Hove beach.
Mr Gove said there was "evidence to suggest" there has been a lower level of compliance for some young people.
He said it might be that some of the messages and channels the government has used have not reached some segments of the population, adding: "It may be that young people feel that they are less likely to be affected and less likely to be infected."
Also in the briefing, Mr Gove said that ventilators - in addition to those being made in the UK - had been sourced from abroad, including 300 that arrived from China on Saturday.
He said the government had also secured new non-invasive ventilation capacity with the help of UK manufacturers.
This would help to ensure patients do not need to be placed on invasive ventilators, which involve patients being intubated and supported to breathe with machinery taking oxygen directly into their lungs.
Mr Gove said a team from University College London working with Mercedes Benz have produced a new device which has been clinically approved.
"They produced 250 yesterday, will produce the same number today and tomorrow, rising to 1,000 a day next week," he said.
He branded conspiracy theories spread on social media blaming new 5G masts for the spread of Covid-19 "dangerous nonsense".
In other developments:
- Sir Keir Starmer has been elected as the new leader of the Labour Party, with members learning the outcome via e-mail after a specially planned conference was cancelled
- Up to 4,000 prisoners in England and Wales could be released from jails in England and Wales early because of the coronavirus, the prison service said
- Two members of staff at Pentonville Prison in north London have died after suffering from Covid-19 symptoms, according to the Prison Officers' Association
- Thirteen residents at a Glasgow care home have died in one week following a suspected outbreak of coronavirus
- Mobile phone masts in Birmingham and Merseyside have been set on fire over false claims linking coronavirus to 5G
- Aldi has said it will lift purchase restrictions on almost all of its products from Monday - with the exception of hand wash, shower gel and UHT milk
- An NHS trust has been told it will have to pay almost £10,000 a month to provide families with free phone calls during the pandemic
- An increasing number of councils are instructing dog owners to ensure their pets are always on a lead in parks and open spaces
- Official data on testing in hospitals suggests that England is lagging behind Scotland, Wales and Northern Ireland
- The British Embassy in Manila has announced a plan to repatriate about 600 UK nationals stuck in the Philippines, after thousands of Britons became stranded around the globe amid the pandemic
- The Queen is due to make a rare special address to the nation on TV, radio and social media at 20:00 BST on Sunday