Archaeologists in Ukraine have unearthed the remains of an ancient pyramidal structure that pre-dates those in Egypt by at least 300 years. The stone foundations of the structure, which probably resembled Aztec and Mayan ziggurats in South America, were discovered near the eastern city of Lugansk.

It is thought they were laid about five millennia ago during the early Bronze Age by animists who worshipped a sun god. The "pyramid" is in fact a complex of temples and sacrificial altars topping a sculpted hillside with steps on its sides.

Viktor Klochko, head of the excavation, said the discovery was of international significance. "This is the first monument of its age and kind found in eastern Europe," he told the Guardian. "It changes our whole conception of the social structure and the level of development of the cattle breeders and farmers who were the direct ancestors of most European peoples."

There are about 100 pyramids in Egypt, and the remains of Mesopotamian pyramids are preserved in Iraq and Iran. Ziggurats are also found in Mexico, and the Nubians built pyramids as burial sites for monarchs in the Nile valley. But pyramid structures are rare in Europe. One of the few is a Roman-era pyramid near Nice, France, that may have been built by legionnaires involved in an Egyptian cult.

Although graves have been found at the Lugansk site, archaeologists think it was used for sacrifice by burning, rather than as a burial ground. "People lived in the surrounding valleys and climbed up it to carry out their ceremonies," said Mr Klochko. "They had a pagan cult that bowed down to the sun, as did the ancestors of the Slavs."

Remains of sacrifice victims, ashes and ceramics have been found at the site, but no jewellery or treasure. The complex, which covered three-quarters of a square mile and was around 60 metres (192ft) high, was probably used for 2,000 years.

"What surprised me most is the scale of this enormous complex," Stanislav Mogilny, a student working on the excavation, told Russian television. It's just incredible - a titanic feat."