A 20-year-old mother accused of sorcery has been burnt alive in front of hundreds of people in Papua New Guinea.

Gruesome photos of Kepari Leniata being burnt to death yesterday in Mt Hagen, in the Western Highlands, feature on the front pages of both the country's national dailies.

Witch burning has become common in PNG, but it is not normally so public.

The National said relatives of a boy she was accused of killing tortured her with a hot iron rod, stripped her naked, tied up her hands and legs and threw her into the fire.

She is said to have admitted under torture to killing the 6-year-old boy through sorcery after he died at the Mount Hagen General Hospital on Tuesday.

Police and hospital staff who arrived at the scene of the fire could not save her.

Witnesses told The National that the relatives of the boy stripped the woman before marching her to a junction, where she was thrown onto a pile of burning tyres.

The Post Courier said hundreds of onlookers watched on.

"The torture and brutal murder of a mother of two provided a photo opportunity for many of the onlookers, including school children, who crowded around and took photos of the woman being consumed alive by the fire," the report said.

Several policemen at the scene were helpless to do anything to save the women because they were outnumbered by the perpetrators and their supporters.

Provincial police commander Superintendent Kaiglo Ambane condemned the killing. He said police were treating the case as murder and would charge those responsible.