BEIJING, December 13 (Xinhua) -- A government think tank has warned that 2013 may see continued rises in real estate prices and face the risks of market collapses in some localities.

According to a green paper on China's housing sector released by the Chinese Academy of Social Sciences (CASS) on Thursday, the academy is worried that many indexes of the country's housing market have shown rising trends in recent months.

According to a report by the National Bureau of Statistics on December 9, ?China's real estate investment rose 16.7 percent year on year in the first 11 months of this year, compared with 15.4 percent in the first 10 months.

The green paper said housing prices in most of Chinese cities will continue rapid increases in the fourth quarter of this year and into 2013, and real estate bubbles in some cities will burst due to a retreat of investment and speculative funds.

Some small- and medium-scale real estate companies' fund chains will break, which will leave more unfinished buildings and financial risks in the country, it added.

The green paper expressed the CASS's belief that, while the Chinese government's macro-control policies implemented in restraining speculation in real estate have worked, they have not achieved optimal results.

It said one reason why the policies had not worked as intended was some local governments' loose implementation of the directives.