The 30,000-year-old site was found near America's gateway - close to the Bering Strait between Russia and Alaska.

Writing in Science journal, the authors said they found stone tools, ivory weapons and bones of butchered animals.

The artefacts are twice as old as those in Monte Verde in Chile, site of the Americas' most ancient human life find.

The site in Arctic Siberia showed that ancient hunters lived on the Yana River, not far from the Bering land bridge that then connected Asia with North America.

The scientists said that, while much of what is now Europe, Canada and the northern United States was covered in ice, the Yana area was ice free.

It was a dry flood plain, without glaciers, that was home to mammoth, horse, musk ox and other animals.

"Abundant game means lots of food," writes Julie Brigham-Grette of the University of Massachusetts. "It was not stark tundra as one might imagine."

Daniel Mann of the University of Alaska said the evidence "makes it plausible that the first peopling of the Americas occurred prior to the last glacial maximum", about 20,000 to 25,000 years ago.

Donald Grayson, a paleoanthropologist at the University of Washington in Seattle, said the find was significant because it was far earlier than previous evidence from that part of the world.

"Until this site was reported, the earliest site in the Bering land bridge area was dated at about 11,000 years ago," he was quoted by the Associated Press news agency as saying.

"Every other site that had been thought to have been early enough to have something to do with peopling of the New World has been shown not to be so."