O'Riordan's publicist also released a statement saying, "Family members are devastated to hear the breaking news and have requested privacy at this very difficult time."
But it gave almost no details about the singer's death.
O'Riordan battled a bad back and other health issues last year that forced The Cranberries, which released the acoustic album "Something Else," to cancel a tour of Europe and North America. She also revealed she had been diagnosed with bipolar disorder.
Her last public words appeared to be a Tweet from Dec. 20 in which she said she was "feeling good" and performing again, and another from Jan. 3 in which she announced "We're off to Ireland."
The youngest of seven children, O'Riordan hailed from the city of Limerick and launched her musical career in 1990 when she successfully auditioned to be the singer of a band then called The Cranberry Saw It.
With a Celtic-inspired singing style that sometimes included yodeling and a thick Limerick accent she made no attempt to hide, O'Riordan powered the band's best-known hits such as "Zombie" and "Linger."
"It threw into question what a voice could sound like in that context of rock," the Irish singer Hozier said in a tweet. "I'd never heard somebody use their instrument in that way."
Over the course of their career, The Cranberries sold more than 40 million albums worldwide. In 1995, Rolling Stone hailed the band as ""Ireland's biggest musical export since U2."
The Cranberries went on hiatus in 2003 and reformed in 2009. O'Riordan also branched out on her own, recording several solo albums and also providing the vocals for a New York City-based alternative band called D.A.R.K.
Raised by devout Catholics, O'Riordan was an admirer of Pope John Paul II and performed at several of the Vatican's annual Christmas concerts.
|Dolores O'Riordan greets Pope John Paul II at the Vatican on Dec. 14, 2001. |
The Pope had a private audience with singers performing the next day in a Christmas Concert. Reuters file
As word of O'Riordan's death spread, Irish President Michael Higgins weighed-in with condolences. "To all those who follow and support Irish music, Irish musicians and the performing arts her death will be a big loss," he said.
Tributes also poured in from other musicians and her many fans.
O'Riordan is survived by her ex-husband, former Duran Duran tour manager Don Burton, and her three children, Taylor Baxter, Molly Leigh and Dakota Rain, according to The Irish Times.