NHS England has told major trauma centres to prepare for a second terrorist attack this Bank Holiday weekend.
The national clinical director for trauma Chris Moran urged staff in 27 cities to be ready for an incident, in a letter obtained by the Health Service Journal.
The threat level for a terrorist attack in the UK remains at the highest possible level following the bomb blast at an Ariana Grande concert in Manchester on Monday.
The letter asked that all staff had easy access to their major incident plan, as well as instructing them to carry identification at all times.
They were also urged to ensure they knew what to do in case their hospital was placed on "lock down".
Eighteen adults and 14 children are still receiving treatment in Manchester hospitals following Monday's explosion, which put emergency staff under intense pressure.
Five adults and five children remain in a critical condition, according to Central Manchester University Hospitals NHS Trust.
In total, the NHS said 116 people had received care with 75 having been admitted to eight hospitals.
Suicide bomber Salman Abedi detonated a homemade nail bomb in the foyer of the Manchester Arena following a concert by US singer Ariana Grande on Monday night.
The attack killed 22 people including an eight-year-old girl, and parents who had been waiting to collect their teenage children.
In his letter Mr Moran praised Manchester hospitals, writing: "The trauma community in Manchester has provided a tremendous response to the atrocity on Monday night and this is a credit to their dedication and clinical skills and also the preparation that has taken place."
The letter continued: "You will be aware that we have a bank holiday weekend approaching.
"There are a number of things that all trauma units and major trauma centres can do to prepare for a further incident and I should be grateful if you could disseminate these within your network so that front-line clinicians are aware."
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