Queen was the rock on which modern Britain was built: Truss

British Prime Minister Liz Truss, who was appointed by Queen Elizabeth II just 48 hours earlier, said on Thursday that the United Kingdom is "devastated" by her death and described the late monarch as "the rock on which modern Britain was built".

Queen Elizabeth II, the UK's longest-serving monarch, died on Thursday at Balmoral Castle in Scotland after reigning for 70 years. She was 96.

Her death brings to an end the longest reign in the history of the United Kingdom, and one of the longest reigns by any head of state.

"We are all devastated" at the news of the Queen's death, which is a "huge shock to the nation and the world," Truss said.

She described the Queen as "a rock on which modern Britain was built", adding: "Britain is the great country it is today because of her."

She said the Queen was a personal inspiration to her as well as many Britons.

"Her devotion to duty is an example to us all," Truss, who had an audience with the Queen on Tuesday, said in a statement outside 10 Downing Street.

The Queen came to the throne in 1952 and witnessed enormous social change. Her reign of 70 years was seven years longer than that of Queen Victoria.

With her death, her eldest son and heir Charles will lead the country in mourning as the new King and Head of State for 14 Commonwealth realms.