BEIJING - China is on a drive to register all its citizens, including those born illegally under the one-child policy, so they qualify for the "hukou" papers that allow access to social welfare.

According to 2010 national census data, China has around 13 million unregistered, or "black," citizens. Local authorities may have refused to register children born in breach of the family planning policy, or parents of such children may have not registered them out of fear of punishment.

The "black" population also includes people without a birth certificate, children born out of wedlock, orphans adopted outside the official system, and people pronounced missing or dead.

The General Office of the State Council said on Thursday that it will "remove illegal restrictions to citizens' rights to a hukou," ordering local authorities to register children irrespective of the legality of their birth.

Chinese need hukou for medical insurance, basic education and other social benefits.

The Chinese government has been "working vigorously" to register unregistered citizens, according to a statement jointly issued by China's police, civil affairs, education, social security and health and family planning authorities on Thursday.

The statement called for hukou registration to be provided for everyone, regardless of the reasons for them not currently having one. "No organization or individual is allowed to deny citizens their rights in this regard," it said.

The government will ensure that previously unregistered children and adults get all the benefits due to them, the statement also said.