Scientists hunting for fossils of giant rats in East Timor stumbled on unique rock carvings up to 12,000 years old, Australia's research agency said.

The experts were digging in Timor's Lene Hara cave, a treasure trove of fossils and rock art, when they chanced upon a group of stylised human faces etched in the rock.

"Looking up from the cave floor at a colleague sitting on a ledge, my head torch shone on what seemed to be a weathered carving," said Ken Aplin of Australia's Commonwealth Scientific and Research Organisation (CSIRO).

"I shone the torch around and saw a whole panel of engraved prehistoric human faces on the wall of the cave."

The face carvings, which include one with a circular headdress resembling the sun, are the first of their kind to be found in Timor and the only ones from the Pleistocene period (ending 12,000 years ago) in the region.

"The local landowners with whom we were working were stunned by the findings. They said the faces had chosen that day to reveal themselves because they were pleased by the field work we were doing," Aplin said.

Other art in the cave has been dated at around 30,000 years old, while CSIRO last year said it had discovered evidence of an extinct species of ancient, giant rats the size of small dogs.