London, Jun 3 (IANS): The UK's Queen Elizabeth II will not attend the Jubilee service at St Paul's Cathedral after experiencing discomfort while watching the parade at Buckingham Palace the previous day.

The four-day Jubilee celebrations which mark the Queen's 70-year reign began on Thursday.

The 96-year-old monarch appeared twice at Buckingham Palace balcony, flanked by other senior royals, as they watched a military parade and waved at thousands of well-wishers gathered on The Mall, reports the BBC.

Later in the evening, she took part in a beacon lighting ceremony.

Hours after the ceremony, the Buckingham Palace confirmed she would not attend Friday's thanksgiving service, but said she "would like to thank all those who made today such a memorable occasion".

The decision was made with "great reluctance" after considering the "journey and activity required", the Palace added.

The BBC report said that the next Jubilee event the Queen is due to attend is the derby at Epsom race course on Saturday.

But there was no confirmation of her participation yet.

Friday's service will give thanks for the Queen's seven decades as monarch.

The largest church bell in the UK, the 16-tonne Great Paul, will ring continuously for four hours after the service.

Senior royals including the Prince of Wales, Duchess of Cornwall and the Duke and Duchess of Cambridge will all attend, with Prince Charles officially representing the Queen.

The Duke and Duchess of Sussex, who have flown over from California, will also join.

It will be Prince Harry and Meghan's first royal event together since leaving the UK two years ago.