UN Secretary-General Antonio Guterres warned Monday of the clear and present danger of nuclear weapons, according to Anadolu Agency.

"Nuclear weapons, and the threat of their use, are not confined to history books. They have once again appeared in the daily rhetoric of international relations,” Guterres said in a message to mark the 79th anniversary of the atomic bombing of the Japanese city of Hiroshima by the US.

"They represent a real and present danger that remains with us today,” he added.

The Aug. 6, 1945 bombing of Hiroshima during World War II left an estimated 140,000 people dead by the end of the year, while an atomic bomb dropped on the city of Nagasaki three days later killed an estimated 74,000 people.

"The lessons of Hiroshima, which once guided our collective efforts towards disarmament and peace, have been pushed aside," Guterres said.

While "some are recklessly rattling the nuclear saber once more," he stressed that the UN endeavors to keep alive the lessons of 1945.

He called on the world to stand together to condemn "this unacceptable behavior" and find new solutions to bring disarmament to life.

"We will never forget the lessons of 6 August 1945. No more Hiroshimas. No more Nagasakis," he added.