A scientists' group moved the hands of its symbolic Doomsday Clock to five before midnight, one minute closer to a possible apocalypse, in response to increasing risks of nuclear and environmental disaster.

The clock was last moved in January 2010, when it was eased back from five to six minutes before midnight.

"Two years ago, it appeared that world leaders might address the truly global threats that we face," the Bulletin of the Atomic Scientists said. "In many cases, that trend has not continued or been reversed."

The clock now shows the same setting as in 2007.

"Faced with clear and present dangers of nuclear proliferation and climate change, and the need to find sustainable and safe sources of energy, world leads are failing to change business as usual," said Lawrence Krauss, co-chair of the group's board of sponsors.

Several of its key recommendations had not been addressed, including better control and transparency of the nuclear industry, and more aggressive action to cut carbon emissions.