The Hong Kong developer, Lai Fung Holdings, acquired the site in 2007, but the plan to transform it into a commercial-residential complex had been held up due to concerns about the heritage value of the historic buildings. Why the developer suddenly had them demolished remains unclear, but the controversial move triggered an outcry in the local media and among members of the public. Many expressed regret that Guangzhou had lost more cultural relics that harked back to a precious period of its past.

Guangzhou authorities said the demolition was illegal and promised to investigate the issue and punish those involved.

But those concerned about local culture and history were in for another shock two days later.

At midnight on June 14, five ancient tombs in suburban Luogang district were destroyed by workers building Guangzhou's No6 subway line. The Qin dynasty tombs were about 2,000 years old.

The Beijing-based quoted Miao Hui, a researcher at the Guangzhou Institute of Culture Relics and Archaeology, as saying: "We were digging the tombs yesterday. But by this morning, we found that all five tombs were gone."

Local media said archaeologists started their field work in March and had planned a three-month excavation of the site, ending in August.

By June 14, they had found 18 ancient tombs built between the Shang dynasty and the Warring States period, three of which contained ancient artefacts. The archaeologist used red string to demarcate the areas where the tombs had been found and hung warning signs reading "archaeological digging area".

The string and signs proved no match for bulldozers sent by the government-backed construction company working on the subway line.

However many cultural relics have been ruined on the mainland in the past three decades during its headlong rush for economic development, the situation could be about to get worse, with the "Great Leap Forward of land development" about to be taken to a new level in what Premier Li Keqiang has called the "Township Construction Movement". It will see millions of farmers moved from villages to new towns, with villages levelled and whole areas rebuilt.

Any cultural relics yet to be identified by archaeologists will simply disappear.

The Guangzhou authorities said they would investigate the destruction of the tombs and launch a major campaign to double-check all valuable relics recorded by the government to make sure they were safe. The officials also said they would teach developers to respect the city's past and its traditions.

But the prospects that the campaign will succeed appear slim. The No6 subway line that led to the destruction of the Qin dynasty tombs will connect two suburban areas in northwest and northeast Guangzhou with the city centre. It's the type of project that is expected to proliferate once the "Township Construction Movement" kicks off in earnest. Beijing and many local governments regard this movement as a straw they can grasp to shore up declining economic growth. Chen Xiwen, director of the central government's rural work office, told a conference late last year that "township construction" would be the new engine of economic growth in the coming decade. So what are the chances that Guangzhou's city government can save historic sites at a faster rate than developers destroy them?

People may argue that a rich city like Guangzhou could spend more to preserve its cultural relics. But, ironically, it is possible that the more money a city has, the more aggressive its development plan might be, leading to even quicker loss of valuable historic sites.

Even if Guangzhou is determined to preserve sites, the number of construction managers and workers far exceeds the number of archaeologists and it remains an uneven race.

Residents of the city, the Pearl River Delta and the mainland as a whole are best advised to take pictures of every cultural relic, old building and historical ruin they see in rural areas.

It may be the last chance they will get.