BEIJING - A government official in charge of family planning has pledged to make further efforts to improve the country's gender imbalance.

Authorities will crack down further on illegal prenatal gender tests and selective abortions, which are believed to be the primary causes of the gender imbalance, according to Wang Xia, head of the National Population and Family Planning Commission (NPFPC).

Authorities have investigated 15,000 cases and punished 13,000 people for violating family planning laws since the launch of a special campaign by six government departments in 2011, Wang said.

The government plans to bring China's gender ratio below 115 newborn males for every 100 females by 2015. The target will not be easy to reach, as the majority of China's provinces have a much higher ratio, Wang said.