"It is almost impossible to describe how much I adored Joan and how much she has meant to me. She was not only the funniest woman I have ever met but was incredibly loving, honest, and lived her life with no regrets," Rancic said in a statement issued to E! News.

Rivers' death was announced by her daughter Melissa saying her mother's "greatest joy in life was to make people laugh. Although that is difficult to do right now, I know her final wish would be that we return to laughing soon," Wet Paint reported.

Rancic sent her condolences to Rivers' daughter and grandson, saying: "Melissa and Cooper who have lost something that can never be replaced. Their bond was truly one-of-a-kind. They had the greatest mother and grandmother anyone could ever hope for."

On Monday, Rancic celebrated her wedding anniversary with her husband, Bill Rancic, the first winner of Donald Trump's "The Apprentice." The two tied the knot in Italy in 2007, Inquisitr reported.

On the other hand, Osbourne took to Twitter to share a photo of her holding up a red sign that read 'Why I am in the hospital' in an undisclosed hospital just hours before she learned about Rivers' death.

"When you have a cough go to the doctor or you will end up like me! #Pneumonia," Osbourne captioned the photo.

Later on, the 29-year-old TV presenter wrote on Facebook, "I'm completely heartbroken by the loss of my beloved Joan."

Kotsiopoulos also took to Twitter to pay tribute to Rivers.

"Rest in peace @Joan_Rivers. Thank you for changing my life. I will miss you so much," Kotsiopoulos tweeted.