72 years ago, U.S. dropped first atomic bomb on Hiroshima, helping end WW II

 
An aerial view of Hiroshima, Japan, after the atomic bombing  on Aug. 6, 1945 during World War II. The city was practically obliterated with 80,000 people killed immediately and another 60,000 within the year.

Sunday marks a somber anniversary -- the day the U.S. dropped the atomic bomb on Hiroshima, Japan on Aug. 6, 1945, 72 years ago.

A B-29 bomber named the Enola Gay dropped the bomb called "Little Boy," killing 80,000 Japanese people and injuring another 35,000, according to History.com. Another 60,000 people are estimated to have died within a year from injuries and radiation sustained in the bombing.

Three days later, the U.S. dropped a second atomic bomb on another Japanese city, Nagasaki, effectively ending World War II.

Since then, nuclear proliferation has created a dangerous modern world, with many nations now capable of using nuclear weapons on their neighbor.

The United Nations issued a statement Sunday urging countries to continue working toward a nuclear weapons-free world.

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The annual ceremony at the Peace Memorial Park in Hiroshima on Sunday, Aug. 6, 2017 commemorating the atomic bombing of Hiroshima on Aug. 6, 1945. This year marks the 72nd anniversary of the world's first atomic bombing that killed 140,000. Hiroshima's appeal of "never again" on the 72nd anniversary has acquired renewed urgency as North Korea moves ever closer to acquiring nuclear weapons.

Ryosuke Ozawa/AP

"The states possessing nuclear weapons have a special responsibility to undertake concrete and irreversible steps in nuclear disarmament," United Nations Secretary General António Guterres said in a message delivered for him at the annual memorial Saturday in Hiroshima, Japan.

The U.N. estimates nations around the world still have some 15,000 nuclear weapons in their arsenals.