Stars including Mariah Carey and Simon Cowell have paid tribute to Whitney Houston after her sudden death in a Beverly Hills hotel room.

Mariah, who recorded the duet When You Believe with Houston in 1998, wrote on Twitter: "Heartbroken and in tears over the shocking death of my friend, the incomparable Ms Whitney Houston.

"My heartfelt condolences to Whitney's family and to all her millions of fans throughout the world.

"She will never be forgotten as one of the greatest voices to ever grace the earth."

Music mogul Simon Cowell described Houston as "one of the greatest singers of all time" and a "true superstar".

Country singer Dolly Parton, whose song I Will Always Love You became Houston's biggest hit, said in a statement: "Mine is only one of millions of hearts broken over the death of Whitney Houston.

"I will always be grateful and in awe of the wonderful performance she did on my song and I can truly say from the bottom of my heart, 'Whitney, I will always love you. You will be missed'."

Houston's godmother Aretha Franklin spoke of her shock, writing on Twitter: "I just can't talk about it now, It's so stunning and unbelievable. I couldn't believe what I was reading coming across the TV screen."

Houston's ex-husband Bobby Brown, also a singer, last night was said to have broken down as he took the stage before a sell-out crowd in Mississippi. "First of all, I want to tell you that I love you all. Second, I would like to say, I love you Whitney. The hardest thing for me to do is to come on this stage."