In a major discovery for understanding the origins of the universe, US scientists say they have detected echoes of the Big Bang 14 billion years ago.

The "first direct evidence of cosmic inflation," or the rapid growth spurt that came in the first moments of the life of the universe, was found with the help of a telescope at the South Pole, and was announced by experts at the Harvard-Smithsonian Center for Astrophysics.

The detection of these gravitational waves represents the last untested element of Albert Einstein's general theory of relativity, filling in a major gap in our understanding of how the universe was born.

The waves are ripples that move through space and time, and have been described as the "first tremors of the Big Bang." Their detection confirms an integral connection between quantum mechanics and general relativity.

"Detecting this signal is one of the most important goals in cosmology today. A lot of work by a lot of people has led up to this point," said John Kovac, leader of the BICEP2 collaboration at the Harvard-Smithsonian Center for Astrophysics.

The telescope targeted a specific area of sky known as the "Southern Hole" outside the galaxy where there is little dust or extra galactic material to interfere with what humans could see with the potent sky-peering tool.

By observing the cosmic microwave background, or a faint glow left over from the Big Bang, small fluctuations gave scientists new clues about the conditions in the early universe.

The gravitational waves rippled through the universe 380,000 years after the Big Bang, and these images were captured by the telescope.

"The South Pole is the closest you can get to space and still be on the ground," said Mr Kovac.

"It's one of the driest and clearest locations on Earth, perfect for observing the faint microwaves from the Big Bang."

Rumours of the landmark discovery began to circulate Friday, as the hastily convened press conference was first announced.

However, scientists said they spent three years analyzing their data to rule out any errors.

"This has been like looking for a needle in a haystack, but instead we found a crowbar," said co-leader Clem Pryke of the University of Minnesota.

Harvard theorist Avi Loeb said the findings provide "new insights into some of our most basic questions: Why do we exist? How did the universe begin?

"These results are not only a smoking gun for inflation, they also tell us when inflation took place and how powerful the process was," Loeb said.

According to theoretical physicist Alan Guth, who proposed the idea of inflation in 1980, described the latest study as "definitely worthy of a Nobel Prize."

"This is a totally new, independent piece of cosmological evidence that the inflationary picture fits together," Mr Guth, of the Massachusetts Institute of Technology, was quoted as telling the journal Nature.