Sinéad O'Connor: Tributes flow for Irish singer dead at 56

Tributes have flowed for the "radical and incredible" Sinéad O'Connor after the Irish singer's death at 56.

She had a voice that "cracked stone", said English musician Alison Moyet, while British band Massive Attack spoke of the "fire in her eyes".

English singer Jah Wobble told the BBC the singer and activist had had "the essence of a Celtic female warrior".

Her family announced the death "with great sadness" on Wednesday. The cause of death was not made public.

The Grammy-winning singer shot to international stardom in 1990 with the hit ballad Nothing Compares 2 U, and released 10 studio albums between 1987 and 2014.

She had a difficult childhood, being placed as a teenager in Dublin in one of the notorious former Magdalene laundries, originally set up to incarcerate young girls deemed to be promiscuous.

A protester against child sexual abuse in the Catholic Church, in 1992 she faced controversy after ripping up a picture of Pope John Paul II on US TV show Saturday Night Live.

Personal tragedy overshadowed her life with her 17-year-old son Shane found dead in January of last year. In one of her final tweets, she called him "the love of my life, the lamp of my soul".

Moyet paid tribute to O'Connor's "astounding presence" and voice that "cracked stone with force by increment". "As beautiful as any girl around and never traded on that card. I loved that about her. Iconoclast," she said on social media.

"Devastated," Massive Attack said. "Honestly, to bear witness to her voice, intimacy in the studio. On the road every single person stopped - dropped their tools during soundtrack. The fire in her eyes made you understand that her activism was a soulful reflex and not a political gesture."

O'Connor sang on Jah Wobble's album Rising Above Bedlam and he played on her song The Last Day Of Our Acquaintance.

Speaking to Newshour on the BBC World Service, the singer remembered a "very special person". Her voice was "very powerful, very controlled... there was a sweetness and fragility to it", he said. But it was "no secret... that there was a degree of sadness".

"There are no words," REM lead singer Michael Stipe simply said in his tribute.

US singer-songwriter and pianist Tori Amos remembered "such passion, such intense presence and a beautiful soul, who battled her own personal demons courageously".

The Pogues singer Shane MacGowan and his wife Victoria Mary Clarke said: "We don't really have words for this but we want to thank you Sinéad for your love and your friendship and your compassion and your humour and your incredible music."

Singer Yusuf Islam - formerly known as Cat Stevens - called O'Connor, like himself a convert to Islam, a "tender soul".

Belfast filmmaker Kathryn Ferguson said she was "devastated" by the news as she had been working on a documentary film about O'Connor, called Nothing Compares, which is set to be released this Saturday.

"Her album, the Lion and the Cobra, was played on repeat as we drove around Belfast... And it became this visceral soundtrack to my early childhood. And then, in the early '90s, my friends and I felt like we really discovered her for a second time, and could really see how she looked, heard what she had to say. And she became this huge icon of ours and someone we were so proud of, and that she was from Ireland, Ireland. So she had a huge impact on me as a young Irish teenager."

"She is one of the most radical, incredible musicians that we've had." Ferguson said. "And we were very, very lucky to have had her."

Political figures also paid tribute to O'Connor, including Irish President Michael D Higgins as he said: "One couldn't but always be struck by the depth of her fearless commitment to the important issues which she brought to public attention."