Si Xue, an 11-year-old girl in Southwest China's Sichuan Province, rarely sees her mother and father since they migrated to Guangzhou, capital of South China's Guangdong Province, in search of work.

A fifth-grade pupil at Fuqiao village primary school, Si has been living with her grandparents since she was in kindergarten.

Every month, her parents send her 500 yuan ($65) to cover her living expenses. That's quite a lot of money for a kid in the countryside, but Si said she misses her mom and dad more and more every day.

Si is part of the lonely group known as China's "left-behind" children.

The wave of urbanization that has swept across China in the past few decades has brought more than 120 million farmers into cities in search of work. However, they often leave their children behind, in the care of a single parent, grandparent or other relatives.

Officials with the All-China Women's Federation estimate that there are about 20 million of them.

To help these children, the federation, in conjunction with a dozen other government bodies, including the Education, Justice and Finance ministries, jointly launched a campaign to protect the rights and interests of left-behind and migrant children over the weekend.

The goal of the "Same Sky" campaign is to develop a support network for such children, said Gu Xiulian, the federation's chairwoman.

The Finance Ministry has urged local governments to set aside funds from their annual budget to take care of such children.

And the Ministry of Justice has been researching ways to make parents more responsible for their children's welfare.

Grassroots civil affairs departments have been urged to promote community services for migrant and left-behind children.

"Left-behind children often face difficulties with their health, education, psychology and morality," Gu said.

The Lin sisters, aged 8, 10 and 12, offer one example of the problems such children can face. The girls have been living without their parents in a remote village in central Guangdong. All three of the girls have been badly injured since their parents left to work in Shenzhen in 2000.

Lin Wenrong, the middle sister, has been known as the "ghost child" ever since she was badly burnt by a fire that broke out as she was trying to cook for herself four years ago.

Some left-behind children also face serious financial difficulties when their parents fail to send them money in a timely manner.

"The most serious problems are actually psychological ones because these children's families are incomplete," Sun Yunxiao, director of Chinese Youth Research Center, wrote on his blog.

"Because they lack any sort of family education, these children are more likely to suffer from psychological problems like loneliness and insecurity, and they feel ignored. They are also more likely than ordinary children to perform poorly at school, or even commit crimes," Sun said.

To address the absence of parental love and care, schools and other segments of society are doing more to help raise left-behind children.

Boarding schools and homes for left-behind children have been built in Qingshen County, Sichuan Province.

"At the beginning of every term, teachers at primary and middle schools investigate each child's family background. The left-behind children are noted and receive special attention," said Cai Gang, head of the county, where 8,000, or 40 percent, of the children younger than the age of 16 have been left behind.

Editor: Yan