Soul superstar Stevie Wonder used his set at the Global Citizen Festival in New York on Saturday (28Sep13) to call for gun laws in the U.S. to be tightened. The Superstition hitmaker was one of the headliners at the Central Park concert, which aims to help tackle poverty worldwide, but he also drew fans' attention to the hot-topic weapons ownership debate. He declared to the crowd of 60,000, "We must do something about the gun laws in this country," before noting that John Lennon was gunned down nearby in 1980 - and then performing the Beatles icon's world peace anthem Imagine. During his set, Wonder also invited onstage Ban Ki-moon, the secretary general of the United Nations, as well as singers Janelle Monae and Maxwell, according to The New York Times. The 63-year-old singer was the final act of the five-hour concert, following sets by John Mayer, Alicia Keys, Kings of Leon, and Elvis Costello. In July (13), Wonder vowed never to perform in Florida again until a controversial self-defence law is abolished following the acquittal of George Zimmerman, who gunned down teenager Trayvon Martin in February, 2012.