The spread of nuclear weapons technology is "an outrage to all humanity" in an unstable world of terrorism networks and increasing violence in the name of religion, the head of the largest alliance of World churches has said

Rev Samuel Kobia, general secretary of the World Council of Churches, did not mention any specific country in his report to delegates and observers representing nearly every branch of Christianity. But he told reporters before the speech that his remarks were aimed at both nations with nuclear arms and others, such as Iran that may be seeking to acquire them.

He also singled out Iran's leading critic — the United States — with warnings that it remains vulnerable to terrorism and that economic and technical advances in once-poor countries are chipping away at its status as the world's sole superpower. "Nuclear proliferation is an outrage to all humanity," Kobia told clerics, scholars and religious activists gathered for meetings aimed at strengthening bonds and plotting new priorities for the group's more than 350 member churches.

"The recent reports of countries acquiring nuclear weapons technology is frightening. But it is equally a scandal that countries which possess vast arsenals of nuclear weapons are unwilling to renounce their use," Kobia said.

The United States and other nations accuse Iran of seeking to develop nuclear arms, but Tehran says its atomic programme is only for energy production.

Kobia, a Methodist pastor from Kenya, cited the United States as a lesson that no nation is immune to the "new era" realities: terrorism, religious divides and natural disasters amplified by climate change.

"How can we talk of any country as a superpower when the government cannot protect its people from terrorism, from natural disasters, from preventable diseases?" he said.

His wide-ranging address also touched on some of main issues facing delegates before the conference ends Feb. 24: global warming, dialogue with Muslims, internal rifts over gay clergy, and the rapid growth of evangelical-style churches outside the World Council fold.

The WCC comprises mainline Protestants, Anglicans and Orthodox churches. The Roman Catholic Church is not a member, but takes part in many forums and had top envoys at the 10-day meeting in Brazil. The assembly hopes to conclude with declarations intended to set new objectives for member congregations.