When China announced its massive stimulus plan, the package was aimed at putting the economy back on a long-term growth trajectory - not stoking another property boom.

But fears are growing that the 4-trillion-yuan ($586 billion) financial boost is being siphoned to inflate an unsustainable property bubble.

For many potential homebuyers, house prices were already too high when the package was launched in November last year. Yet the gap between salaries and house prices could widen even further if the record sums now being spent at land auctions are any indicator.

Across the country, property plots known as di wang, or "land kings", are fetching unprecedented amounts in bouts of frenzied bidding.

What has surprised many seasoned analysts, though, is that most of the bidding is being done by State-owned enterprises (SOEs), which have access to vast amounts of cheap financing thanks to the stimulus package.

Of the 10 most expensive land purchases in China's major cities this year, six were made by SOEs.

Last month, Poly Real Estate Group Co Ltd, a leading Chinese property developer and subsidiary of State-owned conglomerate Poly Group, paid 1.79 billion yuan - almost 7,000 yuan per sq m - for a plot in Nanjing, capital of Jiangsu province, making it the city's most expensive piece of land for commercial development.

China Overseas Land and Investment, a development firm listed on the Hong Kong Stock Exchange and a subsidiary of State-owned China State Construction Engineering Corp, in September purchased land in Putuo district of downtown Shanghai for 7 billion yuan, more than 22,000 yuan per sq m. Part of the plot attracted no bidders when it was put up for sale at 1.6 billion yuan in July last year.