Japan's Hiroshima marked the 65th atomic bomb anniversary on Friday, calling for a world free of nuclear weapons. UN Secretary-general Ban Ki-moon attended the ceremony in Hiroshima Peace Park, becoming the first UN chief to attend the annual ceremony. Before Hiroshima, he also for the first time visited Nagasaki, the second Japanese city the United States dropped an atomic bomb on during World War II. Ban was joined by representatives from over 70 countries, including U.S. Ambassador to Japan John Roos, who was the first U. S. representative to do so, and French and British officials. 'I feel honored to be the first U.N. secretary general to take part in the peace memorial ceremony on the 65th anniversary. And I am deeply moved. ... I come here for world peace.' Ban said. 'When the atomic bombs fell on Hiroshima and Nagasaki, I was one year old. Only later in life could I begin to understand the full dimension of all that happened here,' he said. Calling nuclear disarmament and non-proliferation a top priority of his work, Ban said 'the moment has come' for the world to become free of weapons of mass destruction. 'We see new leadership from the most powerful nations. We see new engagement in the U.N. Security Council. We see new energy from civil society.,' he said, adding important progress was made at the nuclear summit in Washington, which 'we will build upon in Korea in 2012'. Hiroshima Mayor Tadatoshi Akiba made a peace declaration at the ceremony, urging Japan to take the lead in the pursuit of abolishing nuclear weapons by 2020. 'Now the time is ripe for the Japanese government to take decisive action,' he said. 'It should begin to 'take the lead in the pursuit of elimination of nuclear weapons' by legislating into law the three non-nuclear principles, abandoning the U.S. nuclear umbrella, legally recognizing the expanded 'black rain areas,' and implementing compassionate, caring assistance measure for all the aging hibakusha anywhere in the world.' A moment of silence was observed at 8:15 a.m., the time of detonation of the atomic bomb over Hiroshima, which killed about 100,000 people in a blink. Also present at the ceremony was Prime Minister Naoto Kan, who vowed to adhere to Japan's three antinuclear principles. On Aug. 9, a second nuclear bomb was dropped on the city of Nagasaki, and six days later, Japan surrendered. In the years since the war, many people have developed diseases that are considered related to exposure to radiation created by the bombs. 