Bystanders, including many children, watched and some took photographs of Wednesday's brutal slaying. Grisly pictures were published on the front pages of the country's two largest newspapers, The National and the Post-Courier, while the prime minister, police and diplomats condemned the killing.

In rural Papua New Guinea, witchcraft is often blamed for unexplained misfortunes. Sorcery has traditionally been countered by sorcery, but responses to allegations of witchcraft have become increasingly violent in recent years.

Kepari Leniata, a 20-year-old mother, had been accused of sorcery by relatives of a 6-year-old boy who died in a hospital on Tuesday. She was tortured with a hot iron rod, bound, doused in gasoline, and then set alight on a pile of car tires and trash in the Western Highlands provincial capital of Mount Hagen, national police spokesman Dominic Kakas said.

Deputy Police Commissioner Simon Kauba on Friday blasted Mount Hagen investigators by phone for failing to make a single arrest, Kakas said. The public were apparently not cooperating with police, and police carrying out the investigation were not working hard enough, Kakas said.

"He was very, very disappointed that there's been no arrest made as yet," Kakas said. "The incident happened in broad daylight in front of hundreds of eyewitnesses and yet we haven't picked up any suspects yet," he added.

Kakas described the victim's husband as the "prime suspect" and said the man had fled the province. Kakas said he did not know if there was a relationship between the husband and the dead boy's family.

He said more than 50 people are suspected to have "laid a hand on the victim" and committed crimes in the mob attack. While many children had witnessed the killing, there were no child suspects, he said.

Kakas said onlookers were shocked by the brutality but were powerless to stop the mob. Police officers were also present but were outnumbered and could not save the woman, he said. There is an internal investigation under way into what action police at the scene took.

Police Commissioner Tom Kulunga described the slaying as "shocking and devilish." "We are in the 21st century and this is totally unacceptable," Kulunga said in a statement. He suggested courts be established to deal with sorcery allegations, as an alternative to villagers dispensing justice.

Prime Minister Pete O'Neill said he had instructed police to use all available manpower to bring the killers to justice. "It is reprehensible that women, the old and the weak in our society should be targeted for alleged sorcery or wrongs that they actually have nothing to do with," O'Neill said.

In Washington, State Department spokeswoman Victoria Nuland condemned Leniata's killing as a "brutal murder." "There is no possible justification for this sort of horrific violence. We urge that sufficient resources are devoted to identifying, prosecuting and bringing to justice those responsible," Nuland said. She added that the U.S. would continue to work with the Papua New Guinean government and civil society to address gender-based violence.

The United Nations' Office of the High Commissioner for Human Rights said the killing "adds to the growing pattern of vigilante attacks and killings of persons accused of sorcery" in Papua New Guinea.

In other recent sorcery-related killings, police arrested 29 people in July last year accused of being part of a cannibal cult in Papua New Guinea's jungle interior and charged them with the murders of seven suspected witch doctors.

Kakas could not immediately say what had become of the 29 since their first court appearances last year in the north coast province of Madang. Police alleged the cult members ate their victims' brains raw and made soup from their joysticks.

The killers allegedly believed that their victims practiced sorcery and that they had been extorting money as well as demanding sex from poor villagers for their supernatural services. By eating witch doctors' organs, the cult members believed they would attain supernatural powers.

Murder in punishable by death in Papua New Guinea, a poor tribal nation of 7 million people who are mostly subsistence farmers. But no one has been hanged since independence.