United Nations, Aug 6 (IANS): UN Secretary-General Antonio Guterres has called for progress toward a world free of nuclear weapons on the occasion of the 76th anniversary of the August 1945 atomic bombing of Hiroshima during the World War II.

On August 6, 1945, the US dropped an atomic bomb on Hiroshima and a second on Nagasaki three days later, killing about 210,000 people by the end of that year.

The nuclear attacks eventually brought about the end of Japan's colonisation and invasion of many East Asian countries, and the end of World War II.

"I am deeply concerned by the lack of progress toward the goal of a nuclear-free world," he said in a video message for a ceremony to mark the anniversary.

States in possession of nuclear weapons have been modernising their arsenals in recent years, sparking a new arms race, but the decisions by Russia and the US to extend the New Strategic Arms Reduction Treaty and engage in a dialogue on arms control "are welcome first steps towards reducing the risk of nuclear catastrophe", the UN chief said.

"I call on all states that possess nuclear weapons to adopt risk reduction measures, individually and jointly," said Guterres.

"The only guarantee against the use of nuclear weapons is their total elimination."