Katherine Jenkins is ''heartbroken'' by her best friend's death.

The mezza-soprano singer is grieving after her close friend Polly Noble succumbed to cervical cancer, seven years after contracting the disease.

The Welsh songbird posted a picture on Twitter of the two of them, writing: ''Heartbroken. Rest in Peace my darling friend.''

And in another photo on her Instagram page, she added: ''Heartbroken - Sleep now with the angels.''

The pair became friends when they were both struggling singers in 2001 and instantly bonded.

Katherine was stunned when she got the call telling her Polly had cancer four years later.

The classical star previously recalled: ''She didn't look or sound ill - it was just unbelievable.

''And of course the word cancer frightens the life out of me because I had watched my father die of lung cancer when I was 15.

''But he had been nearly 70, and Polly was just 24. She was too young; she had too much to live for.''

The tragic news comes two months after Katherine accepted a proposal from writer and director Andrew Levitas, who popped the question during a trip to the Hamptons, New York on April 15.