The Duke of Edinburgh pointed out a bearded man and asked "is that a terrorist?" as he greeted crowds at Sandringham, it has been claimed.
The 96-year-old was attending St Magdalene Church accompanied by the Princess Royal when it is reported he made the comment as he joked with onlookers.
Witnesses who claimed to have heard the comment said the man had a ginger beard, The Sun and the Mail Online reported. Buckingham Palace declined to comment.