In response, unidentified vigilantes, known as ninja due to their all-black garb, killed a number of suspected sorcerers, including religious leaders.
Black magic practiced in Banyuwangi is a mix of animist beliefs and Islamic mysticism which developed from inter-religious conflict during the 16th century Mataram court period.
By November, police in Central Java had detained around 200 mentally ill people, as they were at risk of being attacked if they were out at night and unable to explain themselves.
Two had been seized from a police car by vigilantes who reportedly slit their throats; the third man was beheaded and his head paraded around on a stake.
[1] On 1 October 1998, the Surabaya Post reported "a rumour about the existence of attacks by ninja-like squads" that were targeting "community leaders as well as ulama".
On 4 October 1998, the Jawa Post reported that "prayer teachers are in the sights of groups of dozens of killers who wear all-black clothes and masks like ninjas".
Some have argued that the killings were encouraged covertly by the military in an effort to destabilize the new Indonesian government, or to weaken Nahdlatul Ulama or the emerging Islamic National Awakening Party.