BEIJING, Aug 30 (AP) -- Gay sex was punishable by death under Genghis Khan's rule.

That was among the findings of Chinese researchers who spent more than a year compiling the legendary Mongolian conqueror's code of laws, the official Xinhua News Agency said Thursday.

His early 13th century empire stretched across Asia all the way to central Europe.

Article 48 of the code said men who "committed sodomy shall be put to death," according to experts at a research institute in the Chinese region of Inner Mongolia.

The experts at the Research Institute of Ancient Mongolian Laws and Sociology said the ban was put into place because Genghis Khan wanted to expand the Mongolian population, which was about 1.5 million at the time. The rival Song Dynasty, which dominated today's central China, was 100 million strong, Xinhua said.

The code also said that damaging grassland with unauthorized excavations or starting fires was punishable by death, Xinhua said, without providing details.

Experts compiled the Mongolian code based on historical texts, including Marco Polo's travelogue, Xinhua said. The original text was lost more than 600 years ago.