China has closed melting glaciers in its northwestern Xinjiang region to tourists who littered, polluted and even drove across the ice that provides water to millions, the official Xinhua agency said Saturday.

The glaciers in the Tianshan, or heavenly mountains, supply 2.3 million people in the regional capital Urumqi with drinking water but are shrinking by around 8m a year because of global warming and increased human activity, the report said.

Travel agencies had been offering unauthorised tours that drew around 2000 visitors each year for as little as 20 yuan ($2.53) per person. As well as driving across the ice, careless tourists had damaged research equipment on one of the country's most closely studied glaciers, the report said.

Glaciers covering China's Qinghai-Tibet plateau, known as the ¡°roof of the world¡±, are also shrinking by 7 per cent a year.

China is battling to clean up its heavily polluted waterways and stave off water shortages across arid northern regions that have been exacerbated by waste and mismanagement.

The country's per-capita water resources are less than one-third of the global average, and summer glacial meltwater is crucial to millions of people downstream, who rely on it for irrigation and hydroelectric power.