The activists climbed the 5,137-metre (16,853 foot) mountain, the highest in Turkey and unfurled a banner which read: "G8: This is the point of no return. Save the climate now".

Andree Bohling, the group's climate and energy campaigner said the Group of Eight industrialised nations must commit themselves to significant reductions in greenhouse gas emissions during their June 6-8 summit in Germany.

"We want to see specific and ambitious targets. Anything else is meaningless," Bohling said.

"Bush, Blair, Merkel and other G8 leaders must wake up -- we will not get another chance... Either they act, and act radically, now, or it may be too late for our generation and almost certainly for our offspring," he added.

Tuesday's demonstration comes four days after Greenpeace published a leaked document showing the United States had raised serious objections to a proposed global warming declaration expected to be signed at the G8 summit.

According to the document, the United States rejected the idea of setting mandatory emissions targets, as well as language calling for G8 nations to raise overall energy efficiencies by 20 percent by 2020.

Earlier this month, Greenpeace said its activists were building a model of Noah's Ark on Mount Ararat to raise awareness over global warming and the dangers -- floods, droughts and natural disaster -- it poses for the world.

The ship, built on a side of the mountain, will be unveiled in a public ceremony on May 31.

The Book of Genesis in the Old Testament says God decided to flood the earth after seeing how corrupt it had become, and told Noah to build an ark and fill it with two of every species.

After the flood waters receded, the ark came to rest on a mountain in what is now eastern Turkey and many believe Mount Ararat is the ark's final resting place.