Davy Jones, the British-born singer of 1960s pop group The Monkees, has died at the age of 66 in the US.
Medical officials in Florida did not comment on the cause of death, but a spokesman for the star said he had suffered a heart attack.
The former teen idol had several hits with The Monkees, including Last Train to Clarksville, Daydream Believer and I'm A Believer.
Jones and his cohorts - Micky Dolenz, Michael Nesmith and Peter Tork - sold millions of records after being put together to star in their self-titled TV show between 1966 and 1968.
Micky Dolenz tweeted: "I am in a state of shock and disbelief right now... My heart and prayers go out to Davy's family."
And Mike Nesmith posted a tribute on Facebook saying: "So many lovely and heartfelt messages of condolence and sympathy, I don't know what to say, except my sincere thank you to all. I share and appreciate your feelings."
He added: "David's spirit and soul live well in my heart, among all the lovely people, who remember with me the good times, and the healing times, that were created for so many, including us. I have fond memories. I wish him safe travels."
His manager and brother-in-law Joseph Pacheco paid tribute, describing him as an "incredible human being".
The group split in 1971 but Jones, who lived in Hollywood, Florida, got back together with Dolenz and Tork over the years to play gigs.
Although The Monkees had nine top-40 hits in their heyday, they were criticised for being a manufactured group. Californian band The Byrds mocked them in their single So You Want To Be A Rock 'n' Roll Star.
However, they made efforts to prove themselves by writing more of their own songs and starring in a 1960s cult film, Head, with Jack Nicholson.
In the early 1960s, Jones had appeared as Ena Sharples' grandson in Coronation Street and also starred in British police series Z-Cars.
He briefly left showbusiness to train as a jockey - and would continue to race horses later in life - but returned to acting with a role in a stage production of Oliver!
From the West End he followed the show to Broadway where he built up an acting career and went on to audition for The Monkees.
Jones is survived by his third wife, Jessica, and four daughters.
In a statement his publicist, Helen Kinsick, said he died near his passion - his horses - and was an integral part of the community, involved in philanthropy.