Britain's 95-year-old Queen Elizabeth II tested positive for Covid-19 on February 20 but her symptoms are "mild" and she intends to continue with light duties at her Windsor Castle residence, aides said.

The news comes after Prince Charles, the queen's eldest son and heir, tested positive on February 10, two days after meeting his mother at Windsor.

No information was given then on whether Queen Elizabeth – who this month marked 70 years on the throne – had taken any Covid tests herself.

She resumed in-person audiences at the castle last week, but complained to one attendee of suffering from stiffness and was photographed holding a walking stick.

"Buckingham Palace confirm that the queen has today tested positive for Covid," a statement from the palace said.

"Her Majesty is experiencing mild cold-like symptoms but expects to continue light duties at Windsor over the coming week," it said.

"She will continue to receive medical attention and will follow all the appropriate guidelines."

While normally secretive about the queen's health, the palace has previously confirmed she is fully vaccinated against Covid-19.

Britain's Press Association said "it is understood a number of cases have also been diagnosed among the Windsor Castle team".