US musician and former Velvet Underground frontman Lou Reed has died at the age of 71.
The singer-songwriter, whose best-known tracks included Perfect Day and Walk on the Wild Side, was considered one of the most influential in rock music.
The Velvet Underground became known for their fusion of art and music and for collaborating with Andy Warhol.
According to the Associated Press news agency, Reed's literary agent said he died of a "liver-related ailment".
An admitted hard drinker and drug user for many years, Reed had a liver transplant this May after cancelling five California concerts scheduled for April.
"I am a triumph of modern medicine," Reed posted on his website on 1 June.
"I look forward to being on stage performing, and writing more songs to connect with your hearts and spirits and the universe well into the future."
The Velvet Underground never achieved commercial success during their 1960s existence, but their influence on music in later decades was widely recognised.
The punk, glam and alternative rock movements of the 1970s, '80s and '90s were all indebted to Reed, whose songs were covered by the likes of REM, David Bowie, Nirvana, Patti Smith and countless others.
Music producer Brian Eno once summed up their influence by saying: "The first Velvet Underground album only sold 10,000 copies, but everyone who bought it formed a band."
The group were inducted into the Rock and Roll Hall of Fame in 1996.
After quitting The Velvet Underground in 1970, Reed released his self-titled debut in 1972, but it wasn't until the Bowie-produced LP Transformer later that year - which featured both Perfect Day and Walk on the Wild Side - that brought him chart success.
As a solo artist, he released 20 studio albums. His last, Hudson River Wind Meditations, was released in 2007.
He is survived by his second wife, the musician and performing artist, Laurie Anderson.