Mary Travers, one third of the hugely popular 1960s US folk group Peter, Paul and Mary, has died after a battle with leukaemia aged 72.A statement on the group's website said the singer succumbed "to the side effects of one of the chemotherapy treatments" she was undergoing.She had been suffering from leukaemia for several years.Peter, Paul and Mary had hits including If I Had a Hammer, Lemon Tree and Puff, The Magic Dragon.They became known for their mixture of liberal politics with folk music that won them a loyal following of fans and also five Grammy Awards.Bandmate Peter Yarrow said that in her last months, Travers handled her declining health "in the bravest, most generous way imaginable".He added that throughout her long career, Travers sang with honesty and complete authenticity."I believe that, in the most profound of ways, Mary was incapable of lying, as a person, and as an artist - that took great courage, and Mary was always equal to the task."Noel "Paul" Stookey, the trio's other member, praised the singer for her inspiring activism, "especially in her defence of the defenceless.""I am deadened and heartsick beyond words to consider a life without Mary Travers and honoured beyond my wildest dreams to have shared her spirit and her career," he said.Travers was an outspoken supporter of the civil rights and anti-war movements.The group travelled the world and frequently appeared at political rallies and demonstrations, including the March on Washington in 1963.Travers kept up her activism after Peter, Paul and Mary broke up in the early 1970s. She performed as a solo artist before the trio later reunited for benefits and other concerts.She underwent a successful bone marrow transplant to treat her leukaemia and told The Associated Press in 2006 she was "feeling fabulous".But by mid-2009, Yarrow told a Washington radio station that the singer's condition had worsened again and thought she would no longer be able to perform.Travers is survived by her husband, Ethan Robbins and daughters, Alicia and Erika.Credit: BBC