The singer Joni Mitchell has been rushed to hospital in Los Angeles after an ambulance was called to her Bel Air home.

"Joni has been hospitalised," a statement on the Rock and Roll Hall of Fame singer's official website said.

"We are awaiting official word on her condition and will post it here as soon as we know."

Celebrity website TMZ quoted unnamed sources as saying paramedics were called to the 71-year-old musician's home around 2.30pm local time.

She is thought to have been unconscious at the time, it said.

It remains unclear what prompted the emergency call, although Mitchell is being treated in intensive care.

The Canadian singer is best-known for hits like Big Yellow Taxi, which was famously covered by Counting Crows, and Both Sides Now.

Sky News US correspondent Greg Milam, who is in Los Angeles, said Mitchell has spoken openly about health issues in recent years, including the effects of decades of heavy smoking on her voice.

Mitchell has received eight Grammy Awards, including a lifetime achievement award in 2002.

She was inducted into the Rock and Roll Hall of Fame in 1997.