Mayors of the only two cities ever attacked with atomic weapons, survivors of the explosions in 1945 and relatives of Japanese nationals abducted by North Korean agents blasted Pyongyang on Tuesday for conducting its third nuclear test despite strong international calls not to do so.

"This is an insult that tramples upon the feelings of (people in) atom-bombed areas desiring a world without nuclear weapons," Nagasaki Mayor Tomihisa Taue said in a statement, calling the action a "threat to global peace and security."

Taue told reporters in Tokyo that the "use of a nuclear test as a tool for international negotiations is totally unacceptable."