Sharia law ... A woman is caned in Aceh for selling food during Ramadan in October. A woman and a man will soon be caned publicly for adultery.

Sharia law ... A woman is caned in Aceh for selling food during Ramadan in October. A woman and a man will soon be caned publicly for adultery. Photo: AFP

Sharia police in the Indonesian province of Aceh will publicly flog a young woman for adultery after she was turned in by eight vigilantes who had already gang-raped her as punishment.

The woman, a 25-year-old widow, and her alleged partner, a married 40-year old man, were caught inside her home last Thursday by a group of eight who were intent on enforcing the sharia prohibition on sex outside marriage, local media reports say.

The eight, who included a 13-year-old boy, tied up and beat the man and repeatedly raped the woman before dousing both in raw sewage.

They then marched the couple to the office of the local sharia police.

Ibrahim Latif, the head of the sharia police, or Wilayatul Hisbah in the town of Langsa, in Aceh's far south-east, was quoted in The Jakarta Globe saying: "We want the couple caned because they violated the religious bylaw on sexual relations".

Under the sharia law, which is peculiar to Aceh, each of the couple faces nine strokes of the cane in a public place.

The woman's ordeal at the hands of her accusers would not be taken into account in delivering the sentence, Mr Ibrahim said.

"They have to be [caned] as a form of justice … they've confessed to having sex several times before, even though the man is married and has five children".

The Jakarta Globe newspaper reported that Teungku Faisal Ali, the head of the Aceh chapter of the country's largest Islamic organisation, Nahdlatul Ulama had backed the caning.

The organisation is usually considered part of Indonesia's moderate muslim maintream.

However, Mr Faisal said the alleged rapists themselves should be treated more harshly than the couple, because they had "set back efforts to uphold sharia in Aceh".

He said vigilantes should not act directly, but report offences to the sharia police.

Three of the alleged rapists including the boy are in police custody, and police have appealed for the families of the other five to give them up.

They are facing investigation and conviction by the ordinary criminal courts.

Aceh is the only province of Indonesia which enforces sharia law, after the central government in Jakarta granted its religious leaders the right to impose it in 2001 to try to quell separatist sentiment.

A recent bylaw in the province extended its provisions to all residents and visitors, including non-Muslims.

The law is enforced patchily, but Langsa is known to be strict. In nearby Lhokseumawe, women are prohibited from wearing tight jeans and riding astride motor scooters — they are required to go side saddle. Women are also expected to cover their hair, and young unmarried couples are not allowed to sit together in public in case sexual feelings emerge.

The law has often been abused by vigilantes and overzealous officials.

In one tragic case in 2012, a 16-year old girl was at a concert with friends in Langsa when the sharia police harangued her as a prostitute. When local media picked up the story the next day, repeated the accusation and published her full name, the girl hanged herself.

In 2010, three sharia policemen raped a 20-year-old university student after they found her riding a motorcycle with her boyfriend.