Police in Papua New Guinea have charged two people over the killing of a woman who was burned alive in front of hundreds of people, including young children, after being accused of witchcraft.

Janet Ware and Andrew Watea have been charged with murder over the death of Kepari Leniata, a 20-year-old mother who was stripped, tortured with a hot iron rod, doused in petrol and set alight on a pile of car tyres and rubbish by a mob earlier this month.

Ms Leniata had been accused of sorcery by relatives of a six-year-old boy who recently died in hospital. Ware and Watea are believed to be the boy's mother and uncle, police said.

Police said more arrests are expected over the murder.