BEIJING - Poly Real Estate Group Co, the country's second-largest developer by market value, said on Sunday its first-half net profits surged 71.7 percent year-on-year to 2.8 billion yuan ($437.5 million).

The company's sales revenue increased 35.1 percent to 15.2 billion yuan in the January-June period, it said in its first-half report to the Shanghai Stock Exchange.

From January to June, Poly's transaction value surged to 39.5 billion yuan, a year-on-year increase of 81.4 percent. Its transaction area was up 27.6 percent to 3.41 million square meters.

The company expected China's economic growth to face a bigger challenge in the second half of the year because of the complicated global political and economic environment.

"The sovereign debt crisis in Europe and United States as well as political turmoil in some regions will make the global economic recovery process more uncertain," it said.

Poly said the possibility of "a localized price volatility" in the second half of the year cannot be ruled out because of the Chinese government's efforts to curb housing price surges, increasing supplies and a continuous capital crunch plagued the real estate sector.

According to government statistics, more Chinese cities reported lower or unchanged property prices in July amid renewed government efforts to cool the market.

In July, 31 cities out of the statistical pool of 70 major cities saw new home prices decline or remain unchanged from a month earlier, compared with 26 cities in June.