Tuli Kupferberg, a poet and singer who went from being a noted Beat to becoming, in his words, “the world’s oldest rock star” when he helped found the Fugs, the bawdy and politically pugnacious rock group, died on Monday in Manhattan. He was 86 and lived in Manhattan.

He had been in poor health since suffering two strokes last year, said Ed Sanders, his friend and fellow Fug.

The Fugs were, in the view of the longtime Village Voice critic Robert Christgau, “the Lower East Side’s first true underground band.” They were also perhaps the most puerile and yet the most literary rock group of the 1960s, with songs suitable for the locker room as well as the graduate seminar (“Ah, Sunflower, Weary of Time,” based on a poem by William Blake); all were played with a ramshackle glee that anticipated punk rock.

With songs like “Kill for Peace,” the Fugs also established themselves as aggressively antiwar, with a touch of absurdist theater. The band became “the U.S.O. of the left,” Mr. Kupferberg once said, and it played innumerable peace rallies, including the “exorcism” of the Pentagon in 1967 that Norman Mailer chronicled in his book “The Armies of the Night.” (The band took its name from a usage in Mailer’s “Naked and the Dead.”)