Britain reported a record daily coronavirus toll of 381 on Tuesday, including a 13-year-old boy, more than double the number of nationwide deaths posted in the previous 24 hours.
The boy, who died Monday at King's College Hospital in London, is believed to be Britain's youngest confirmed death in the coronavirus pandemic, with relatives saying he had no underlying illnesses.
The country's previous highest daily toll was 260, recorded on Saturday, with the number dropping to 180 on Monday.
Some 25,150 people have now tested positive for the virus in Britain, including Prime Minister Boris Johnson.
As of 5:00 p.m. (1600 GMT) on March 30, 1,789 people have died, the health ministry said on its Twitter page.
But data published by the Office for National Statistics (ONS) for England and Wales on Tuesday revealed that the true toll could be 24 percent higher.
The government figures cover those who have been taken to hospital and tested for the virus whereas the ONS data is for deaths in the community where COVID-19 is suspected.
The boy's family said Ismail Mohamed Abdulwahab "started showing symptoms and had difficulties breathing" before he was admitted to hospital.
"He was put on a ventilator and then put into an induced coma but sadly died yesterday morning," they said through a family friend, Mark Stephenson, adding: "We are beyond devastated."
Johnson told the cabinet via video link that the rising toll "showed the vital importance of the public continuing to stick to the social distancing guidance which has been put in place by the government."
"The situation is going to get worse before it gets better -- but it will get better," he added.
The government last Monday ordered a three-week lockdown, shutting non-essential shops and services to help reduce contacts and relieve the burden on the National Health Service.
Stephen Powis, medical director for the NHS in England, said that despite the latest fatality figures, overall there were "green shoots" because the rate of infections was slowing.
But he added: "It's really important not to read too much into this. It's early days. We're not out of the woods," he told a daily briefing on the government response to the outbreak.
"And it's really important that we keep complying with those [social distancing] instructions."
Cambridge University professor David Spiegelhalter agreed that "great caution" was needed in interpreting daily figures.
"The extreme day-to-day variation in reported COVID-19 deaths is far more than we would expect from chance variability and must be due to reporting practices," he said.
"Some deaths occurred many days ago, and there seems to be fewer reported over the weekend."
Scientists say the full effects of the lockdown are expected to be seen in two to three weeks, with predictions that life may not return to normal for at least six months.
Britain has braced for an expected surge in coronavirus cases, including setting up a 4,000-bed field hospital at a giant London exhibition center -- one of four across the country.
But senior minister Michael Gove said there was "not a fixed date like Easter when you know that the peak will come".