Veteran US folk singer Richie Havens, who shot to stardom with his distinctive style at the iconic 1969 Woodstock music festival, has died, his agent said. He was 72.

Havens' frenzied rhythmic strumming and searing vocal delivery on "Freedom/Motherless Child" mesmerized the crowds at Woodstock, which became a key symbol of 1960s counter-culture explosion.

The African American singer -- who was only drafted in at the last minute to open the three-day event because other bands didn't have their equipment ready -- later became known for covers of Beatles and other artists' songs.

Havens "was gifted with one of the most recognizable voices in popular music," said the Roots agency in announcing the death, adding: "His fiery, poignant, soulful singing style has remained unique and ageless"

The Brooklyn-born artist, who retired from touring three years ago after more than four decades on the road, died at New Jersey home of a sudden heart attack, the booking agency said.

Industry magazine Billboard, hailing his "distinctive intense, rhythmic guitar style and soulful covers of pop and folk songs," noted that he had one Billboard Hot 100 single, a cover of the Beatles' "Here Comes the Sun."

The song reached number 16 in May 1971. Havens also had 13 albums that charted on Billboard 200, including one in the top 40: 1971's "Alarm Clock," which peaked at number 29.

Among tributes Monday, Michael Nesmith of the Monkees tweeted "A HUGE loss to the music world. Devastating news." Benmont Tench of Tom Petty's Heartbreakers said: "Oh no. Richie Havens. What a voice.

"So unhappy about this."

At Woodstock, "Three Days of Music and Peace" in the Catskill mountains in New York state in August 1969, Havens was originally due to be the fifth act on stage.

But other bands had trouble getting their instruments and equipment to the festival site, so he was asked to open -- and ended up playing for more than two hours, while other artists got ready.

"I opened the Woodstock Festival even though I was supposed to be fifth. I said, "What am I doing here? No, no, not me, not first!" I had to go on stage because there was no one else to go on first," he said.

"The concert was already two-and-a-half hours late. Everyone was at the hotel seven miles away and couldn't get to the stage because the one back road they thought they could take was completely blocked.

"I was alone on stage for two-and-a-half hours before any of the other performers came!"

His performance of "Freedom/Motherless Child" was included in the film of the legendary festival, launching his career into the stratosphere.

As well as Woodstock, Havens played other legendary festivals including on Britain's Isle of Wight and Glastonbury, the Royal Albert Hall in London and Carnegie Hall in New York.

"Even when performing in a Greenwich Village coffeehouse or a small club or regional theater, he was eternally grateful that people in any number turned up each time to hear him sing," his booking agency said.

He is survived by four children and several grandchildren, the Los Angeles Times reported.

"While his family greatly appreciates that Richie's many fans are also mourning this loss, they do ask for privacy during this difficult time," added a spokesman.