The address by Francis was similar to a radio peace appeal by Pope John XXIII in 1962 during the Cuban Missile Crisis.
Leader of Roman Catholic church, Pope Francis has called on Russian President Vladimir Putin to end the war he started in Ukraine.
According to the Pope, the crisis could turn nuclear and have heavy effects for the world.
In an address dedicated to Ukraine and made to thousands of people in St. Peter's Square on Sunday, October 2, Francis condemned Putin's latest annexation of parts of Ukraine and urged Putin to think of his own people in the event of an escalation.
The address by Francis was similar to a radio peace appeal by Pope John XXIII in 1962 during the Cuban Missile Crisis.
It was the first time Francis, made such a direct personal appeal to Putin.
"I'm haunted by rivers of blood and tears that have been spilled in these months,"
"In the name of God end the conflict it is absurd that the world was risking a nuclear conflict.
"My appeal goes above all to the president of the Russian Federation, begging him to stop this spiral of violence and death, even out of love for his own people," Francis said.
"On the other side, pained by the enormous suffering of the Ukrainian population following the aggression it suffered, I address an equally hopeful appeal to the president of Ukraine to be open to a serious peace proposal," he said.
Speaking two days after Putin proclaimed the annexation of nearly a fifth of Ukraine and placed the regions under Russia's nuclear umbrella, Francis also emphasised all countries' right to "sovereign and territorial integrity".
"I strongly deplore the grave situation that has been created in the last few days, with more actions that are contrary to the principles of international law," he said in a clear reference to the annexation.
"This, in fact, increases the risk of an nuclear escalation to the point of fearing uncontrollable and catastrophic consequences on a global level," he said.
In a reference to ethnic Russians living in Ukraine, Francis said it was also necessary to respect "the rights of minorities and (their) legitimate worries".
Francis said it was "anguishing" that the world was learning about Ukrainian geography through names of places such as Bucha, Irpin, Mariupol, Izium, Zaporizhzhia and other places where people had suffered "indescribable suffering and fear".