Gately "tragically died" late Saturday on the island of Majorca, the site said. No details of Gately's death were revealed, but the band said in the statement it was traveling to the island early Sunday morning.
The mysterious death baffled Spanish police and Gately's family and friends, including his partner Andrew Cowles, who was with him when he passed away. Police said there were no signs of violence at the house where Gately was found, a seafront villa overlooking the shore.
"Stephen was the kindest, gentlest soul. We send our love and condolences to his partner Andy and to all his friends everywhere," John said in a statement.
Former Irish Prime Minister Bertie Ahern said Gately's death was "a huge tragedy to Irish entertainment, Irish music and further afield as well."
Boyzone, who hit the top of the European charts in the 1990s, announced a comeback tour last year.