Historians have sounded the alarm after 23,600 registered cultural sites apparently "disappeared" in three years.

The sites were largely erased because of development - swept aside by construction work and infrastructure projects including reservoir and road projects - says a national survey carried out by the State Administration of Cultural Heritage (SACH), the country's top relics protection authority.

SACH has been working on the inventory since 2007 and hopes to have a full list of China's historical sites - including ancient tombs, temples and architecture - by 2011.

As of the end of October, 776,200 historical sites had been surveyed and added to the list, said Shan Jixiang, director of SACH.

The number of surveyed sites bettered the total in 2007 by 550,300.

"Most of the disappeared historical sites were demolished during infrastructure construction, for example, highway and reservoir building," said Liu Xiaohe, deputy director of the survey. "The nation will do all it can to preserve as much as it can."

For example, in 2002, China spent more than 300 million yuan ($44 million) to move the 1,700-year-old Zhangfei temple, which was built in honor of a general in Sichuan province. The temple now stands on higher ground, away from the potential damage of the Three Gorges Dam reservoir.

"What we can do now is try our best to protect the significant sites, like the Summer Palace, while for those less important sites, I am afraid they should give way to economic development," he said.

Experts, however, see another reason for the fall in the number of such sites.

Sun Yuexin, founder of the Chinese Cultural Heritage Protection website, said the number of disappeared relics was as large as it was because there had been false reporting and exaggeration of such sites in the past.

"Some local governments would exaggerate the amount of relics they have, so as to ask for more funds from the central government to protect relics," he said.

Governments at all levels had spent more than 1 billion yuan on the survey, an amount Liu said was still insufficient.

"Considering the human resources, travel expense and equipment the survey requires, we need to spend 300,000 yuan to survey a town," he said. But he didn't how much is needed to complete the survey.

He said it would be nice if more people were employed to protect the sites.

"We have about 800,000 historical sites in China, but only 80,000 people are working for relics' protection. Places like the Palace Museum take up more than 2,000 of them, which means some places have no one to take care of," he said.

The last national survey was carried out in 1983. It failed to issue a final report. The first survey was conducted 1956. It also failed to produce a complete list of relics.