Singer Mariah Carey has sparked engagement rumours with her boyfriend James Packer, who is an Australian businessman and investor.

The "Heartbreaker" singer was spotted wearing a sparkling jewel on her left ring finger when walking hand-in-hand with her beau at his casino here, reports dailymail.co.uk.

Carey was all smiles when entering the venue along with Packer. She sported a plunging black dress and brown sunglasses with her hair straightened.

She paused to lock lips with her boyfriend in front of the crowd outside the casino.

Some onlookers noticed a piece of silverware glittering from Carey's left hand. But it looked far more likely to be the "We belong together" hitmaker's favourite butterfly ring which she's worn for nearly a decade.

One of Carey's fan pages on Facebook claimed the suspicious ring was indeed her butterfly band.

"Mariah Carey's butterfly ring is NOT an engagement ring. She has been wearing it for over a decade.... Please stop with the ill-informed speculation," Mariah Carey Australia fan page wrote.