Authorities in Papua New Guinea (PNG) must take urgent action to prevent 'sorcery'-related killings, Amnesty International said after the brutal murder of a woman accused of using witchcraft to kill a young boy.Twenty-year-old Kepari Leniata was stripped, tied up, doused in petrol and burned alive by relatives of the dead boy in the city of Mount Hagen, local media reported."Those responsible for the shocking torture and killing of this woman must be brought to justice," said Kate Schuetze, Amnesty International's Pacific researcher."But there is far more to be done to tackle this endemic problem in Papua New Guinea, where 'sorcery' is still considered a criminal offence."There have been several reports in recent years of people accused of 'sorcery', in most cases women, being murdered.In July 2012, police reportedly arrested 29 members of a witch-hunting gang who were allegedly murdering and cannibalizing people they suspected of 'sorcery'.In 2009, after a string of such killings, the country's Law Reform Commission proposed to repeal the 1971 Sorcery Act, which criminalizes the practice. 'Sorcery' is also often used as a pretext to mask abuse of women, which was last year described as a "pervasive phenomenon" in PNG by the UN Special Rapporteur on violence against women. "Repealing the Sorcery Act is one of the first steps the authorities must take towards preventing these horrific attacks," said Kate Schuetze."But the problem goes far deeper. The authorities must also crack down on those who are abusing this law, essentially by using it as an excuse to attack people."In PNG customs, 'sorcery' is sometimes believed to account for a sudden or unexplained death or illness, and the person thought to be responsible may be killed. Amnesty International has long-standing concerns about human rights violations against women in PNG, where harmful traditions contribute to the negative stereotyping of women and widespread discrimination against them in almost all facets of society.