BEIJING - With most Chinese provinces experiencing a serious gender imbalance, a government official in charge of family planning has pledged the country will work hard to ameliorate the problem.

Wang Xia, head of the National Population and Family Planning Commission (NPFPC), said 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.

The authorities will also intensify obstetric monitoring of mothers-to-be and the real-name registration of newborn babies, the official said.

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 aims 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.

Wang noted that China's gender imbalance problem is remarkably serious in terms of its persistence, severity and widespread reach.

The bias against females in economic, social and cultural fields is still the root cause of the current gender imbalance, Wang said.

Wang noted that when China was much less developed, boys were favored as stronger laborers.

Wang also pledged more effort to promote gender equality, monitor the gender ratio and share information about it.

A natural gender ratio at birth could be somewhere between 103 and 107 boys to every 100 girls.

However, since fetal ultrasound exams became common in China in the 1980s, the country's boy-to-girl birth ratio has hovered at a high level, reaching a record high of 120.56 in 2008.

Thanks to government measures including the recent crackdown, the ratio has fallen each year since 2009. The gender ratio stood at 117.78 in 2011.

China's gender imbalance has caused a series of social problems including sex crimes, trafficking in women, and difficulty finding a spouse for many men, Wang said.