Pope Francis on Friday renewed calls for global nuclear disarmament, warning that new technology had increased the risk of deadly weapons falling into the hands of terrorists.
"You only have to note that nuclear technologies are spreading, partly because of digital communications, and the instruments of international law have not prevented new states from joining those already in possession of nuclear weapons," Francis told a seminar at the Vatican.
"The resulting scenarios are deeply disturbing if we consider the challenges of contemporary geopolitics, like terrorism or asymmetric warfare."
Francis was addressing a Vatican conference on disarmament that was attended by several Nobel peace prize winners and top UN and NATO officials, against the backdrop of tensions over North Korea's nuclear and missile tests.
Western powers are also increasingly concerned over the possibility of groups like Islamic State getting their hands on the technology that could allow them to manufacture an improvised nuclear device.
Describing the current international situation as marked by a "climate of instability and conflict", the Argentine pontiff said the prospects for disarmament appeared "increasingly remote".
"The escalation of the arms race continues unabated and the price of modernising and developing weaponry, not only nuclear weapons, represents a considerable expense for nations.
"As a result, the real priorities facing our human family, such as the fight against poverty, the promotion of peace, the undertaking of educational, ecological and healthcare projects, and the development of human rights, are relegated to second place."
Citing the memory of the victims and survivors of the Hiroshima and Nagasaki nuclear bombs at the end of World War II, Francis said any new use of such weapons would have "catastrophic humanitarian and environmental effects".
"If we also take into account the risk of an accidental detonation as a result of error of any kind, the threat of their use, as well as their very possession, is to be firmly condemned.
"Weapons of mass destruction, particularly nuclear weapons, create nothing but a false sense of security."
Despite his overall gloomy tone, Francis said he was encouraged by a recent UN vote declaring the use of nuclear weapons illegal, even in warfare.