Thousands of attendees observed a moment of silence on Thursday morning during a ceremony in Hiroshima, Japan, to honor the 70th anniversary of the city's bombing by U.S. forces during World War II.Among those present were Japan's Prime Minister Shinzo Abe, U.S. Ambassador to Japan Caroline Kennedy, and visitors, residents, and 150 other officials, Japan Times reported.The Hiroshima Peace Memorial Ceremony is held each year on Aug. 6 at the city's Peace Memorial Park to commemorate the anniversary of the atomic bombing, and has been an annual event since 1947, two years after the bomb was dropped.