The King and Queen send heartfelt condolences to all those affected by Southport stabbings
The King said he and his wife were "profoundly shocked" to hear of the "utterly horrific incident".
He added: "We send our most heartfelt condolences, prayers and deepest sympathies to the families and loved ones of those who have so tragically lost their lives, and to all those affected by this truly appalling attack."
The Prince and Princess of Wales called the attack "horrid and heinous" adding that they were sending "love, thoughts and prayers to all those involved".
They said on X, "As parents, we cannot begin to imagine what the families, friends and loved ones of those killed and injured in Southport today are going through.
"Thank you also to the emergency responders who, despite being met with the most horrific scenes, demonstrated compassion and professionalism when your community needed you most."