By Hyun Oh and Toru Hanai
HIROSHIMA, Japan (Reuters) - Bells tolled and thousands bowed their heads in prayer in Hiroshima on Thursday at ceremonies marking the 70th anniversary of the world's first atomic bombing while survivors warned about Japan's moves away from its pacifist constitution.
Prime Minister Shinzo Abe and his government are pushing security bills through parliament that could send Japanese troops into conflict for the first time since World War Two, sparking massive protests around the country.
Many with memories of the war and its aftermath are scathing about Abe's steps away from Japan's pacifist constitution in pursuit of a more robust security stance, and survivors of the bombing lambasted Abe at a meeting after the commemoration ceremony.
"These bills will bring the tragedy of war to our nation once again," said Yukio Yoshioka, 86. "They must be withdrawn."
Abe, who in a speech at the ceremony called for abolishing nuclear weapons, replied by repeating his view that the legislation was essential to ensure Japan's safety.
At 8:15 a.m. (2315 GMT), the exact time the bomb exploded on Aug. 6, 1945, the crowd stood for a moment of silence in the heavy summer heat while cicadas shrilled, the Peace Bell rang and hundreds of doves were released into the sky.
Hiroshima Mayor Kazumi Matsui urged that nuclear weapons be abolished and demanded the creation of security systems that do not rely on military might.
"Working with patience and perseverance to achieve these systems will be vital, and will require that we promote throughout the world the path to true peace revealed by the pacifism of the Japanese constitution," he said in a speech.
Many of those gathered for the ceremony renewed their calls for peace.
"My grandfather died here at that time and I keep wondering what he felt then," said Tomiyo Sota. "He was still 21 years old and it pains me to think he died so young."
The Hiroshima bombing, which killed 140,000 by the end of the year, was followed by the atomic bombing of Nagasaki on Aug. 9, 1945, which killed about 40,000 instantly. The war ended on Aug. 15.
(Writing by Elaine Lies; Editing by Edmund Klamann)