Pope Leo on Sunday branded those who wage wars and appropriate the Earth's resources as thieves who deprive the world of a peaceful future, and issued a warning about the use of nuclear energy on the anniversary of the Chernobyl reactor accident.

Ukraine commemorates this Sunday the 40th anniversary of the world's worst nuclear disaster, amid persistent fears that the war Russia has been waging for four years could trigger a repeat of the tragedy.

In his weekly address following the Angelus prayer, the Pontiff stated that the Chernobyl accident had left a mark on humanity's collective conscience.

“It remains a warning about the use of increasingly powerful technologies,” said the Pope, who has just returned from a ten-day tour of four African countries.

“I hope that at all levels of decision-making, wisdom and responsibility always prevail, so that atomic energy can always be used in favor of life and peace,” he added.

Commenting on the day's Gospel, which contained the metaphor of the thief of sheep, Pope Leo said that thieves appear in many forms, citing as examples “superficial lifestyles driven by consumerism,” prejudices, and misguided ideas.

“And let us also not forget those thieves who, by plundering the Earth's resources, by waging bloody wars, or by feeding evil in any of its forms, are simply robbing us all of the opportunity for a future of peace and serenity,” he added.

Leo, the first American pontiff, has drawn the ire of President Donald Trump after becoming increasingly critical of war and despotism.