BEIJING (AFP) - China will relax its one-child policy, state media said Friday, in a major policy shift announced days after the conclusion of a meeting of top Communist Party leaders.

The change to the family planning law will let couples have two children if one of them is an only child, state news agency Xinhua reported, citing a "key decision" made by leaders at this week's gathering, known as the Third Plenum.

Xinhua also reported that China is to abolish its "re-education through labour" system, under which police panels can sentence offenders to years in camps without a trial.

The move was "part of efforts to improve human rights and judicial practices" it said, and came in a detailed reform statement issued after a Communist party meeting, adding it would also reduce "step by step" the number of crimes subject to the death penalty.

The deeply unpopular labour camp system, known as "laojiao", is largely used for petty offenders but is also blamed for widespread rights abuses by corrupt officials seeking to punish whistleblowers and those who try to complain about them to higher authorities.

Under the scheme, people can be sent for up to four years' re-education by a police panel, without a court appearance.

Pressure for change in the system has been building for years. In a high-profile case last year Ms Tang Hui, a mother from central Hunan province, was sentenced to a labour camp for petitioning repeatedly after her 11-year-old daughter was kidnapped and forced to work as a prostitute.

Ms Tang had sought accountability for police officers that she said aided the culprits. She was freed after just over a week following a public outcry.