U2 frontman Bono hailed human rights group Mothers of the Plaza de Mayo during the band's concert in Argentina's capital Buenos Aires on Thursday (03MAR06). The campaigning rocker sang on stage with five of the Mothers - who have campaigned for peace since their children disappeared during the Argentine military dictatorship of the 1970s - and later called on the crowd to work together for a world free from conflict. He said, "Let's work together, left and right, rich and poor, young and old." The Mothers have been fighting to be reunited with their abducted children for 25 years; over 9,000 children who disappeared during the 'dirty war' remain unaccounted for.