The ruins of what is thought to be a huge ancient temple have been discovered by archaeologists diving beneath Lake Titicaca in the Andes between Bolivia and Peru.

An international team of scientists announced the finding this week after making more than 200 dives in Titicaca, which, at 3,800m above sea level, is the world's highest navigable lake.

"We've found what appears to have been a 200-metre-long, 50-metre-wide holy temple, a terrace for crops, a pre-Incan road and an 800-metre-long containing wall," said Lorenzo Epis, the Italian leading the Atahuallpa 2000 expedition. Ceramic artefacts were also found on the lake's floor.

Titicaca has long been the subject of legends about a lost underwater city, but there has been little research because of the logistical difficulties of diving at altitude.

While a submerged city has not been found, Mr Epis said the ruins appeared to be 1,000 to 1,500 years old. It thus predates the Incas and could point to the Tihuanaco people, who lived on Titicaca's shores before becoming part of the Incan empire.

"This means our civilisations have left more footprints than we had thought," said Antonio Eguino, Bolivia's vice-minister of culture. The ruins were found in an area of the lake between the town of Copacabana and the popular tourist destinations of the Island of the Sun and Island of the Moon. The divers followed a submerged road until they arrived at the discoveries, at a depth of about 20 metres.

In addition to the practical difficulties, the research project had to contend with a worried public, who had not been informed of the project. Diving was delayed for four days because of the distrust of the local population on the Island of the Sun, who believe the lake is sacred.

Akakor Geographical Exploring, an Italian cultural association that organised the expedition, first made a trip to Titicaca in 1998 to look at underwater caves and to research diving techniques at high altitude.

Marco Antonio Simi, who was on that expedition, said that the groundwork on pressure levels allowed the group to return this year; most diving technology is based on ocean-bound dives, where pressure levels are very different.

Mr Simi said this was the first time top-level divers and professional archaeologists had investigated Titicaca together, adding that it was rare for specialists of both disciplines to work side by side.

The team was looking for an underwater temple. "What they found was the beginning of what they were looking for," he said.