"I am furious, with them (North Korea) for defying strong protests from the international community, including Hiroshima, the city attacked in an atomic bombing," mayor Tadatoshi Akiba said in a statement, as reported by Jiji Press.
"This means a grave challenge for the international community, which can never be forgiveable," Akiba said.
Hiroshima officials were not immediately available to confirm the report.
Akiba's comments came a day after North Korea vowed to build more nuclear bombs and to start enriching uranium for a new atomic weapons programme, after the UN Security Council called for sanctions over its nuclear test.
The 15-member Council voted unanimously Friday to slap tougher sanctions on the North to cripple its nuclear and ballistic missile programmes.
The North, describing Friday's sanctions resolution as a "vile product" of a US-inspired campaign, said it would never abandon nuclear weapons and would treat any attempt to blockade it as an act of war.
The hardline communist state, in a foreign ministry statement reported by its official news agency, said all new plutonium it extracts would be weaponised.