Members of the royal family gathered in Scotland on Thursday after Buckingham Palace said that doctors were "concerned" about Queen Elizabeth II's health.

Driving the news: The palace said doctors had recommended the Queen "remain under medical supervision" at Balmoral Castle and that the 96-year-old monarch is "comfortable" for the time being.

The big picture: The news comes after the Queen canceled a meeting of her privy council on Wednesday and was told by doctors to rest, per AP.

• Prince Charles, accompanied by his wife, Camilla, traveled to Balmoral Castle by helicopter. Prince William is also en route to Scotland, the Telegraph reported.
• Prince Harry is also traveling to Balmoral, the BBC reported.
• The Queen's other children — Princess Anne, Prince Edward and Prince Andrew — have also arrived at Balmoral, per the BBC.

What they're saying: "The whole country will be deeply concerned by the news from Buckingham Palace," newly appointed Prime Minister Liz Truss wrote on Twitter.

• "My thoughts — and the thoughts of people across our United Kingdom — are with Her Majesty The Queen and her family at this time," she added.
• "The President has been briefed of course this morning and will be updated throughout the day concerning the news out of the United Kingdom," National Security Council spokesperson John Kirby said on a call with reporters Thursday.
• "His and the First Lady's thoughts are solidly and squarely with the Queen today and with her family," Kirby added.