JAKARTA: Officers policing sharia law in Indonesia's Aceh province raped a woman and have committed other rights violations, a human rights group said on Wednesday, calling on the province to repeal sharia bylaws.

The group Human Rights Watch said the woman, a 19-year-old university student, was accused of indecency and detained after being caught with her boyfriend riding a motor bike through a coconut plantation.

She was later raped by three sharia officers, it said. Aceh is the only Indonesian province to have implemented sharia or Islamic laws, though some other areas have introduced sharia-inspired bylaws.

Investors are watching for signs that growing Islamisation could make Indonesia, the world's most populous Muslim country, less tolerant or even lead to violence.

Human Rights Watch said Aceh, the country's westernmost province, should repeal two bylaws, including one obliging men and women to wear modest dress.

The rights group cited its field research between April-May that found the police who are meant to uphold sharia law, known as the Wilayatul Hisbah, had conducted virginity tests and committed rape.

“Indonesia has an obligation to prevent the commission of vigilante enforcement of the sharia laws by private individuals and to protect people from the threat of further violence,” the group said in the report.

“At present, it is failing to satisfy this obligation.”

An Aceh court sentenced two of the three officers and the sharia police chief was removed over the attack, the rights group said, but the woman still suffered from trauma and had not returned to university.

Many victims were too afraid to speak out, it said. The central government has devolved more power to regional authorities to increase autonomy and speed up development.

But in some places, including in the western part of the main island of Java, authorities are using that power to try to bring in a more conservative form of Islam.

Most Indonesians are moderate Muslims. Indonesia is an emerging market favourite but investors could become suspicious about prospects for pro-market reforms and globalisation if the country was to become more conservative, analysts say.