Three people have been detained for digging up part of the Great Wall just days before strict new penalties are introduced to protect China's most famous tourist attraction, Xinhua news agency said.

The men used excavators to take earth from the remains of part of the Great Wall in Inner Mongolia, built at least 2,200 years ago, to use as landfill for a village factory.

"It's just a pile of earth," Erhaihao village head Hao Zengjun was quoted as telling officials from the Municipal Office on Cultural Relics Protection.

The Great Wall, which snakes its way across more than 4,000 miles, receives an estimated 10 million visitors a year, mostly to the tiny portion open to tourists at Badaling, the nearest stretch to Beijing.