Panic over nighttime assaults blamed on "grease devils" has struck across rural Sri Lanka, leading to the deaths of at least three people this week, prompting women to stay indoors and men to arm themselves, police and local media said.

Historically, a "grease devil" was a thief who wore only underwear and covered his body in grease to make himself difficult to grab if chased. But lately, the "grease devil" has become a nighttime prowler who frightens and attacks women.

"The story we hear is he comes and bites young women's necks and breasts. Despite several complaints, the police have failed to act on that and in fact in two places have released the culprits," a 36-year old airline ticketing agent from the Hill Country district of Matale said, speaking on condition of anonymity for fear of upsetting authorities.

Two men whom wary villagers identified as "grease devils" were hacked to death on Wednesday by a mob in the central Sri Lankan village of Kotagala, in a tea-growing area, police said.

A 22-year-old man hunting for a "grease devil" in the jungle died after accidentally stepping an electric trap set for wild boars, the Tamil-language newspaper Sudar Oli said on Friday.

At least 30 incidents have been reported across seven districts from Sri Lanka's east coast and across its tea-growing regions in the central Hill Country. Police have arrested 47 people since last month.

"There is no grease devil as such. It is a human among us with an ulterior motive of stealing or to engage in some illegal activities," police spokesman Prashantha Jayakody said.

Jayakody also said some people with "mental disorders" were posing as grease devils.

The panic has nonetheless been enough to prompt men to arm themselves with clubs and sticks to stand guard at night, and women to stay at home. The public fury over the scare even prompted rioting at a police station.

On Tuesday in the eastern village of Ottamavadi, six people including two police officers were injured in a melee after angry residents stormed a police station after the release of a suspected "grease devil."

Traditional Sri Lankan beliefs about spirits and devils remain strong in some areas, where invocations upon them to cure illnesses or curse enemies are common. Traditional devil masks remain a favorite tourist souvenirs.

State TV stations have been broadcasting a picture of what police says is one suspect, whose face is covered in white greasepaint, with the message that the grease devil is not real.