Britain's 95-year-old Queen Elizabeth II will not attend the COP26 UN climate conference in Glasgow, after "advice to rest" from doctors following an overnight hospital stay, her Buckingham Palace office said Tuesday.

"Her Majesty has regretfully decided that she will no longer travel to Glasgow" for a November 1 reception, the palace said in a statement, adding that she "will deliver an address to the assembled delegates via a recorded video message".

The queen worked a busy schedule in early October but cancelled a visit to Northern Ireland last week on medical advice.

On Thursday, she spent the night at the private Edward VII hospital in London for "preliminary investigations".

The stay  -- her first since 2013 -- and the palace's delay in revealing it have raised fears over her health, given her age. 

But the queen resumed official duties Tuesday, greeting new ambassadors to Britain in video audiences from Windsor castle west of London.

Elizabeth II has reigned since 1952 and will celebrate her platinum jubilee next year.

At almost daily public engagements, she has always appeared in good health -- although she was seen using a walking stick for the first time at a major public event this month.