Mark Ronson expressed his deep sadness at the death of Amy Winehouse yesterday afternoon (July 23)

The DJ and musician collaborated frequently with Amy, who was “like a sister to him”, and co-produced her second and final album, ‘Back to Black’.

He said: “She was my musical soulmate. This is one of the saddest days of my life.”

Amy Winehouse was found dead at her north London flat yesterday at 4pm. The Metropolitan Police have said her death is still unexplained.

Her label at Universal released a statement: “We are deeply saddened at the sudden loss of such a gifted musician, artist and performer. Our prayers go out to Amy’s family, friends and fans at this difficult time.”

After hearing the news of the death of her friend, Kelly Osbourne tweeted: "I can't even breathe right my now I'm crying so hard i just lost 1 of my best friends. I love you forever Amy & will never forget the real you.

“i miss my friend! im going to be off twitter for a while thank you for all your support! #Pray4Amy!”

Nicki Minaj also took to Twitter and expressed her shock: "Please tell me Amy Winehouse didn't die. Is this some sick joke?"

Lily Allen tweeted that her death was “beyond sad” and adding: “She was such a lost soul, may she rest in peace.”

Watch Amy Winehouse perform 'Valerie' live on BBC Sessions: