The activist cut a hole in the granite Memorial Cenotaph dedicated to Hiroshima's 140,000 bomb dead that read, "Let all the souls here rest in peace as we will never repeat this mistake."

Takeo Shimazu, an unemployed 27-year-old affiliated with a right-wing group, turned himself in to police before dawn with a hammer and two chisels and told officers he objected to the word "mistake."

"Why should the Japanese apologize in a monument they built? It is the Americans who committed a mistake," he was quoted as saying by the police.

The vandalism comes less than two weeks before Hiroshima is due to mark the 60th anniversary of the nuclear attack on August 6, 1945.

An annual ceremony to mourn the dead is held in the Peace Memorial Park in front of the Memorial Cenotaph, an arch over a coffin with a register of bomb victims' names.

The memorial was dedicated in 1952 by then mayor Shinzo Hamai who said the "mistake" referred to Japan's militarism and that visitors to the cenotaph should "pledge never again to repeat the same sin."

Current Mayor Tadatoshi Akiba said the defacing of the monument "desecrates the souls of atomic bomb victims."

"It is a crime of the most malicious kind that violates the hearts of the people in Hiroshima and the rest of the world who wish for world peace," Akiba said in a statement. "I feel terrible resentment."

The cenotaph has been under camera surveillance since 2002 when another vandal dabbed it with paint.

The latest vandalism comes amid high tension between Japan and neighboring nations which accuse Tokyo of not showing remorse for atrocities during its conquest of Asia.

The United States dropped atomic bombs on Hiroshima on August 6 and Nagasaki three days later, killing more than 210,000 people instantly or from horrific burns. Emperor Hirohito surrendered on August 15, ending World War II.

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