King's College Hospital in Camberwell, south London, said in a statement Tuesday that the teenager, who tested positive for Covid-19, had died. It said that its "thoughts and condolences" were with the boy's family.
"Sadly, a 13-year old boy who tested positive for COVID-19 has passed away, and our thoughts and condolences are with the family at this time," the statement read. "The death has been referred to the Coroner and no further comment will be made."
According to a breakdown of victims of COVID-10 published by Britain's office of National Statistics, the boy is thought to be the youngest known victim of the novel Coronavirus in the UK.
A fundraiser to cover the costs of his funeral has been set up on the crowdfunding website Go Fund Me by Madinah College, where one of his siblings works. "It is with great sadness to announce that the younger brother of one of our teachers at Madinah College has sadly passed away," the page read, adding that the boy apparently had no pre-existing health conditions and "died without any family members close by due to the highly infectious nature of Covid 19".
The news came as a director at the UK's National Health Service (NHS) said there had "been a bit of a plateau" in British coronavirus cases but that despite these "green shoots... we must not take our foot off the pedal," at the daily Downing Street news conference on Tuesday.
Stephen Powis, National Medical Director of NHS England, added: "This is not a short haul, this is going to take time. It's important that we all stick with it."
The UK recorded a 14% daily increase in coronavirus cases on Tuesday, compared to a 13% increase on Monday. It has now had 25,474 cases and 1,793 deaths, according to figures from Johns Hopkins University.
A 12-year-old girl died from Covid-19 in Belgium on Monday, a spokeswoman for the Belgian Health ministry told CNN.
The Belgian government spokesperson for the fight against coronavirus, Emmanuel Andre, said "it was obviously a very difficult moment emotionally because it concerns a child, it touches the scientific and medical community.
He added that it "is an occurrence that is very rare but that upsets us."
Research by CNN and Global Health 50/50 last week using the available data found that men were 50% more likely than women to die after being diagnosed with Covid-19.
Initial reports of people with severe Covid-19 disease have found that they were likely to have underlying health conditions such as hypertension, cardiovascular disease and chronic lung disease, according to Global Health 50/50.