In Britain, people left flowers outside Kensington Palace.
Tributes are being held across the world as Thursday marks the 20th anniversary of Princess Diana's death.
Read: Woman Who Hired Princess Diana as a $5-an-Hour Nanny: 'I Fell in Love With Her'
Earlier in the day, people were seen gathering at Kensington Palace in London, which was Diana's residence until her death. Supporters left flowers on the gates and cut a cake with her photo on it.
People are also remembering the Princess in Paris, where she was killed in a horrific car crash along with her boyfriend, Dodi Fayed, and driver Henri Paul.
Elton John, Diana’s close friend, posted a photo on Twitter with the caption, "20 years ago today, the world lost an angel."
The singer performed a rewritten version of his hit song "Candle in the Wind" at Diana’s funeral back in 1997
Read: Princess Diana Smashes Sand Castles and Plays Dress Up in Rarely Seen Childhood Videos
Diana’s sons, Princes William and Harry, greeted well-wishers Wednesday before retreating back into Kensington Palace to privately honor their late mother.
Newspapers in England ran a photo of the princes paying tribute to their mom back in 1997, alongside a similar photo taken Wednesday.
Watch: What Was Going Through Princess Diana's Mind the Summer She Died
