UN officials on Thursday marked World Radio Day by calling for harnessing the enduring power of this vital medium to promote gender equality and women's empowerment and to amplify the voice of women over air waves. UN Secretary-General Ban Ki-moon, in his message to mark the Day, underlined the need for radio broadcasters everywhere to promote the voice of women and to enhance the role of women within broadcast organizations. "The airwaves have frequently lagged behind when it comes to gender equality. Not nearly enough women's voices are heard -- either in front or behind the microphone," Ban said. "Not nearly enough stories about women and girls are being told. And women make up only a quarter of the members of the boards of the world's media enterprises." "I encourage radio stations to be more inclusive by equally recognizing women in their staff and in their audience," he said. "Radio can also help dismantle stereotypical and imbalanced programming." "This is an opportunity for everyone," he said. "Let us celebrate this World Radio Day by saluting women in radio today and doing our utmost to nurture the new voices for tomorrow." In 2011, the UNESCO General Conference proclaimed Feb. 13 as World Radio Day, the day United Nations Radio was established in 1946. Radio is the most prevalent mass medium, with the ability to reach up to 95 percent of the world's population. World Radio Day aims to celebrate radio as a medium; to improve international cooperation between broadcasters; and to encourage major networks and community radio alike to promote access to information, freedom of expression and gender equality over the airwaves. This year, the Day has a dual theme: to promote the voice of women over the air waves and to enhance the role of women within broadcast organizations. "Without the voices of more than half the world's population, how can we understand the whole story?" Irina Bokova, director- general of the UN Educational, Scientific and Cultural Organization (UNESCO), said in her message for the Day. Radio is vital for promoting gender equality and the empowerment of women, Bokova said. "From pioneering executives in the early 20th century to those today reporting from conflict zones, women have played a key role in the growth of radio." "As citizen journalists, reporters, producers, technicians and key decision-makers, women are working at every level of the broadcasting industry to ensure the free exchange of opinion, information and ideas over the airwaves," she said. "But there is still much work to do," she said, noting that less than one quarter of radio stories are about women, and women represent less than one-third of all top-level management and governance positions in media."