Japan is marking the 71st anniversary of the atomic bombing of Hiroshima by renewing calls for a nuclear weapons free world.

Hiroshima Mayor Kazumi Matsui says world leaders should follow President Barack Obama and learn first-hand about the evils of nuclear weapons.

Obama in May paid tribute to 140,000 people killed by the world's first atomic bomb attack that was dropped by the U.S. to force Japan's capitulation in World War II. Obama became the first sitting U.S. president to visit Hiroshima.

Another atomic bombing three days after Hiroshima killed more than 70,000 people in Nagasaki.

About 50,000 people attended the ceremony Saturday at Hiroshima's Peace Park near the bomb's epicenter.