The cemetery of more than 500 Chinese pilots who were killed in the War of Resistance against Japanese Aggression (1937-45) was recently revealed to have been in ruins for at least the past six years in Kunming, Yunnan Province.

The deceased Chinese pilots were said to have fought side by side with the Flying Tigers, the American Volunteer Group under the command of Claire Lee Chennault, who recruited pilots from the US army, navy and marine corps to help Chinese soldiers fight Japanese forces during World War II.

Sun Guansheng, head of the Yunnan Flying Tigers Research Institute, told the Global Times on Tuesday that coffins were severely destroyed, skeletons exposed and bones scattered around the site when the cemetery was first discovered in 2007, and that situation remains to date.

Trash was also found at the site due to visitors' ignorance of it as a graveyard, reported the Kunming-based City Express on Monday.

The deceased Chinese pilots were previously buried with almost 300 US pilots from the Flying Tigers at a different site. The bodies of the US pilots were sent back home after the end of the war.

"The graves had to be moved to the current site in 1953 as local authorities planned to use the original site to build a barn, and the destruction to the graves has never stopped in the years since," Sun said, noting that the graveyard had been robbed several times and once even caught fire.

Two monuments were set up by the institute in 2008 to mark the graves and mourn the martyrs, but there's been hardly any progress on protecting the site in the following years.

Sun said the institute urged local authorities several times to reconstruct the cemetery, by making plans and construction drawings, but the government hasn't approved their petition yet.

"We have no idea why the authorities still take no moves after all these years," Sun said. "No protection measures have been carried out by them. The environment of the graveyard has not got any better."

Phone calls to Kunming Civil Affairs Bureau, which manages all cemeteries in the city, went unanswered on Tuesday.

The ruined scene of the graveyard was exposed by media reports in 2010, when authorities from the bureau said that the process of protecting the grave was underway. They added that they had started negotiating on the planning of the land but also noted that building cemeteries requires very strict approval procedures.

More than 3,000 Chinese and American pilots were killed during the war. The story of the Flying Tigers has been recorded in many books and later adapted into movies.

"The sacrifice of these martyrs should not be ignored," Sun said, noting that the institute has organized memorial activities every year and the number of people visiting the site has been increasing.  

The lack of protection for historic sites from the War of Resistance against Japanese Aggression has been frequently exposed. Authorities in Jinan, Shandong Province aroused public criticism when zoning a mass graveyard for residential use in April this year, which ensured the return of a monument that was earlier removed from the site.