Queen Elizabeth II has tested positive for COVID-19, just days ahead of an anticipated lifting of all pandemic restrictions in England.

The monarch, who is 95 years old, is experiencing "mild cold-like symptoms" but is expected to continue "light duties" at Windsor Castle during the coming week, Buckingham Palace said in a statement.

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

The queen is thought to have spent time with her oldest son and heir, Prince Charles, just days before he tested positive for COVID-19 for the second time on Feb 10. Charles' wife Camilla, the duchess of Cornwall, also tested positive for the virus on Feb 14.

The queen's health has been a concern since October, when she canceled a trip to Northern Ireland and was admitted to hospital. She followed doctors' orders to rest for several months, before taking up public engagements again at the beginning of February, when she attended a charity event.

On Feb 6, the queen became the first British monarch to celebrate a Platinum Jubilee, marking 70 years on the throne. Various events are planned for later in the year to mark the occasion, culminating in a series of celebrations during a special four-day holiday weekend in June.

UK Prime Minister Boris Johnson reacted to the queen's diagnosis on Twitter on Sunday afternoon.

"I'm sure I speak for everyone in wishing Her Majesty the Queen a swift recovery from COVID and a rapid return to vibrant good health," he said.

Earlier, Johnson had confirmed the government plans to release its so-called plan for living with COVID-19 this week. London is expected to lift all COVID-19 restrictions from as early as Thursday, including the scrapping of a law that requires people to self-isolate for a minimum of five days following a positive COVID-19 test.

"COVID will not suddenly disappear, and we need to learn to live with this virus and continue to protect ourselves without restricting our freedoms," Johnson said on Twitter. "Thanks to our successful vaccination program and the sheer magnitude of people who have come forward to be jabbed, we are now in a position to set out our plan for living with COVID this week."

The government had previously intended to lift restrictions in late March and the decision to bring plans forward has been criticized by many politicians as well as disease experts.