Pope Francis has issued a card showing a 1945 photo of victims of the Nagasaki nuclear bombing in a stark New Year warning over the threat of global conflict.

The Vatican is to print and distribute copies of the image, which shows a young Japanese boy carrying his dead brother on his shoulders to a cemetery, with the words ”the fruit of war” written on the back.

The picture was taken by US Marine photographer Joe O’Donnell shortly after American forces dropped atomic bombs on Japan at the end of World War Two.

The cards issued by Francis will also carry his own signature along with a caption: “The young boy’s sadness is expressed only in his gesture of biting his lips which are oozing blood.”

Mr O’Donnell spent four years documenting the aftermath of the US bombing of Nagasaki and Hiroshima.

His picture was circulated by the Vatican press office ahead of the the Roman Catholic Church’s World Day of Peace, which is celebrated every 1 January.

Vatican analyst John Allen said “the gesture is consistent with Francis’s effort since his election to speak out against what he describes as a ‘Third World War’ today, being fought in piecemeal fashion in various parts of the world.”

Pope Francis leads a mass to mark the World Day of Peace in Saint Peter’s Basilica at the Vatican (REUTERS)

In a post on Catholic blog Crux, he wrote: “The pontiff has also spoken about the disproportionate suffering children often experience in conflicts, including the risk of being enrolled as child soldiers.

“The gesture with the photo of Nagasaki also comes at the close of a year in which the threat of nuclear conflict once again had the world on edge, in light of North Korea’s threat to use nuclear weapons, and US President Donald Trump’s vow that America would unleash ‘fire and fury’ should that happen.”

Nagasaki marks 71st anniversary of atomic bombing

In a New Year’s Day speech to 40,000 people in St Peter’s Square, the Pope criticised Mr Trump’s intention to build a wall along the US border with Mexico and said politicians who stoked fear of migrants were sowing violence and racism.

Pope Francis described migrants and refugees as the world’s “weakest and most needy,” adding: “Please, let us not extinguish the hope in their hearts, let us not suffocate their hopes for peace.