Two more Nightingale hospitals are to be opened to help deal with the rising number of coronavirus cases, the NHS has said.
The new sites, in Bristol and Harrogate, will provide up to 1,500 extra beds for patients with Covid-19.
Similar hospitals are also due to open at Birmingham's National Exhibition Centre and Manchester's Central Complex.
A 4,000-bed facility at London's ExCel centre is due to open later.
The new hospitals will be used to treat patients from around their respective regions.
In Bristol, 300 beds with ventilators will be available at the University of the West of England, with capacity to treat up to 1,000 people in total.
Harrogate Convention Centre will be used for 500 beds - the first of the field hospitals to be built outside a city.
NHS England chief executive Simon Stevens said they would add to "surge capacity".
"We're giving the go-ahead to these additional sites, hoping they may not be needed but preparing in case they are," he said.
"But that will partly depend on continuing public support for measures to reduce growth in the infection rate by staying at home to save lives."
The military helped to set up London's Nightingale hospital, which has 500 beds in place with space for another 3,500.
Staff from across the NHS will be working there, including student nurses, medical students who have started work early and former doctors, nurses and other staff who have come out of retirement.
Health Secretary Matt Hancock said: "The NHS and the military have achieved something extraordinary in setting up NHS Nightingale, London, in only a matter of days.
"It is testament to their hard work and dedication that an additional four hospitals will be rolled out across the nation."
NHS England said it had already freed up more than 33,000 beds around the country, the equivalent of 50 new hospitals.
A deal has also been struck with the independent hospital sector to provide 8,000 extra beds, as well as staff and equipment, it added.
The number of people with the virus who have died in the UK has risen by 569, taking the total to 2,921 as of 17:00 BST on Wednesday.
The government has been criticised for not increasing testing, including screening medics so that those self-isolating unnecessarily can return to work.
On Thursday, it was announced that the UK was aiming to carry out 100,000 coronavirus tests a day by the end of April.