Sinead O’Connor, the gifted Irish singer-songwriter who became a superstar in her mid-20s and was known as much for her private struggles and activism as for her fierce and expressive music, has died at 56.

“It is with great sadness that we announce the passing of our beloved Sinead. Her family and friends are devastated and have requested privacy at this very difficult time,” the singer’s family said in a statement. No cause was disclosed.

Recognisable by her shaved head and with a multi-octave mezzo-soprano of extraordinary emotional range, O’Connor began her career singing on the streets of Dublin and soon rose to international fame.

She was a star from her 1987 debut album, The Lion and the Cobra, and became a sensation in 1990 with her cover of Prince’s ballad “Nothing Compares 2 U”, a seething, shattering performance that topped charts from Europe to Australia and was heightened by a promotional video featuring the grey-eyed O’Connor in intense close-up.

“Nothing Compares 2 U” received three Grammy nominations and was the featured track on her acclaimed album, I Do Not Want What I Haven’t Got, which helped lead Rolling Stone to name her Artist of the Year in 1991.

O’Connor’s other musical credits included the albums, Universal Mother and Faith and Courage, a cover of Cole Porter’s “You Do Something to Me”, from the AIDS fundraising album Red Hot + Blue, and backing vocals on Peter Gabriel’s “Blood of Eden”. She received eight Grammy nominations and in 1991 won for best alternative musical performance.

She was a lifelong nonconformist – she said she shaved her head in response to record executives pressuring her to be conventionally glamorous.

A critic of the Roman Catholic Church well before allegations of sexual abuse were widely reported, O’Connor made headlines in October 1992 when she tore up a photo of Pope John Paul II while appearing on NBC’s Saturday Night Live and denounced the church as the enemy.

O’Connor announced she was retiring from music in 2003, but continued to record new material. Her most recent album was I’m Not Bossy, I’m the Boss, released in 2014, and she sang the theme song for Season 7 of Outlander.

In 2018 O’Connor converted to Islam and adopted the name Shuhada’ Davitt, later Shuhada Sadaqat — although she continued to use Sinead O’Connor professionally.