The family of a 13-year-old boy, believed to be England's youngest reported coronavirus victim, said they have been left "beyond devastated" by his death.
Ismail Mohamed Abdulwahab's loved ones said to their knowledge he did not have any underlying health conditions.
His death at King's College Hospital in London was confirmed by the trust after the UK saw its biggest day-on-day rise in the number of deaths since the outbreak began.
A total of 1,789 patients had died overall in UK hospitals as of 5pm on Monday, the Department of Health said, up by 381 on the day before.
NHS England confirmed that a 19-year-old had died after testing positive for Covid-19.
The Italian chef, named by news website La Repubblica as Luca Di Nicola, was at that stage believed to be England's youngest victim who died in hospital with no existing medical issues.
Ages of victims are not being routinely released elsewhere in the UK.
Cabinet minister Michael Gove on Tuesday described the sharp rise in UK deaths from coronavirus as "deeply shocking" but said he could not say exactly when the peak of the epidemic would come.
NHS England's medical director Professor Stephen Powis warned that while there are "green shoots" signs that the rate at which people are becoming infected with Covid-19 is slowing, the country is still "very much in the woods".
Prof Powis, who joined Mr Gove at the daily Downing Street press conference, said: "We have had a rise in the number of new UK cases but recently there is a little bit of plateau.
"It's really important not to read too much into this.
"It's early days, we're not out of the woods, we're very much in the woods.
"The number of infections is not rising as rapidly as it once was.
"So green shoots, but only green shoots and we must not be complacent and we must not take our foot off the pedal."
Prof Powis said the rate of hospital admissions was still increasing, as was expected at this stage of the epidemic.
However, he said if the number of infections started to drop, then in the next few weeks the "hope" was that the number of admissions would also begin to fall.
Looking to the future, Mr Gove said: "There's not a fixed date like Easter when you know that the peak will come, it depends on the actions of all of us."
He said despite signs that interventions were working, "now is absolutely not the time for people to imagine there can be any relaxation or slackening" of lockdown measures.
It comes as critics said not enough was being done to test NHS frontline staff quickly.
Some 10,767 people are currently in hospital in England, with 3,915 of those in London and 1,918 in the Midlands, where hospital admissions are accelerating.
Turning to testing, Mr Gove said a "critical constraint" on the ability to rapidly increase testing capacity in the UK is the availability of chemical reagents.
He said Prime Minister Boris Johnson and Health Secretary Matt Hancock were working with companies worldwide to ensure the UK gets the material needed to increase tests "of all kind".
The Government has faced serious criticism over testing, with fewer than 10,000 tests being carried out per day on average, despite claims this target had been hit.
Officials have said the target of 25,000 tests per day will most likely not be met for another month.
The Department of Health and Social Care said as of 9am on Tuesday, a total of 143,186 people have been tested, of which 25,150 tested positive.
The Royal College of Physicians, the Royal College of Nursing and the British Medical Association have all said testing of frontline staff is desperately needed.
Mr Gove said the UK must go "further, faster" to ramp up coronavirus testing capacity.
On the issue of ventilators, Mr Gove said the UK was buying them from EU nations and had also placed orders at home.
UPDATE on coronavirus (#COVID19) testing in the UK:
As of 9am 31 March, a total of 143,186 people have been tested of which 25,150 tested positive.
As of 5pm on 30 March, of those hospitalised in the UK, 1,789 have sadly died. pic.twitter.com/ctiAd1ty9p
- Department of Health and Social Care (@DHSCgovuk) March 31, 2020
The first new ventilator devices will roll off the production line this weekend and be delivered to the NHS next week, Mr Gove said.
It comes as other figures revealed that the true death toll is higher than hospital statistics suggest.
Data from the Office for National Statistics (ONS) for England and Wales shows there were 24% more deaths relating to Covid-19 up to and including March 20, compared to hospital-only data for the same period.
The ONS looked at all deaths where Covid-19 was mentioned as a factor, including hospital deaths and those in the community and care homes.
A total of 210 deaths in England and Wales for the time period had Covid-19 mentioned on the death certificate, compared with 170 coronavirus-related deaths reported by NHS England and Public Health Wales.
Hospital figures are of people who have tested positive for Covid-19, whereas the ONS includes all deaths where Covid-19 is mentioned on the death certificate, even if only suspected.
However, the ONS data does provide a much wider picture of what may be happening in the community.
This morning I chaired the first ever digital Cabinet.
- Boris Johnson #StayHomeSaveLives (@BorisJohnson) March 31, 2020
Earlier, Mr Johnson chaired a meeting of his Cabinet by videolink as he continues to self-isolate in Downing Street after testing positive for coronavirus.
The Prime Minister told the meeting: "The situation is going to get worse before it gets better – but it will get better."
In Wales the rise in deaths was seven to 69, in Northern Ireland six to 28 and in Scotland a rise of 13 to 60.