Marianne Kearney, Jakarta – Muslims in Aceh who do not wear Islamic dress will be barred from urban areas from the middle of this month as the authorities start enforcing the Islamic syariah law.

The Acehnese provincial government yesterday announced they will enforce Islamic dress code as part of syariah law introduced in the province last year.

However, non-government groups fear an unclear definition of "Islamic dress" under the new law will encourage harassment of civilians. Local police will begin conducting checks on whether women and men in cities are wearing Muslim dress from March 15, said provincial secretary Thantawi Ishak.

Muslim men must cover their midriff and shorts must not expose their knees, according to a government announcement in local paper Serambi. As for women, the authorities said they must be entirely covered, except for their face, hands and feet.

But women's and non-governmental groups (NGOs) said the ruling on Islamic dress for women was fraught with ambiguity. This will easily allow police to abuse their power as enforcers of Islamic dress, they claimed.

"If police have the power, guns and authority, then it is easy for them to abuse this. There is already a lot of verbal harassment by police towards young women here," said Ms Suraiya Kamaruzzaman from Flowers, a non-governmental women's group.

Many NGOs have criticised the use of security forces to carry out spot checks in towns and cities to enforce the dress code. "The Indonesian Armed Forces' function is to protect the nation and the police's function is to ensure peace; so why are they carrying out sweeping operations to enforce Islamic law?" asked Ms Suraiya.

Adding to the confusion is disagreement over what constitutes Islamic dress in Aceh. Many NGOs acknowledge that most Acehnese will not object to the new rule requiring Islamic dress – as long as it adheres to the Acehnese version of the dress code.

In most parts of Aceh, young women dressing modestly can be seen combining Muslim dress with Western modifications: Jeans or fashionable slacks are worn with a long sleeved shirt and a scarf, wrapped loosely over the head which might reveal one's hair and neck.

Ms Cut Anirta, who works for an international non-government group in a small town in North Aceh, said that in places such as Bireuen, "Muslim dress" for women meant slacks, a loose flowing blouse and a scarf. "In Bireuen, young girls wear jeans and a long blouse with a scarf or jilbab if they're not married. When they are married, they wear the Muslim dress so I don't think it will be a problem," she said.

But for others, Islamic dress follows the style of the Middle East – a long flowing gown is worn with loose slacks and a jilbab or tudung – an Islamic headscarf.

Traditionally in Aceh, lower-class women and women working in the countryside as farmers or market traders merely wore a loose scarf, a sarong and loose shirt, so why should they be forced to change what they already considered to be a devout dress style, asked Ms Suraiya.

Other women were concerned about the punishment for men and women not wearing the Islamic dress. Provincial secretary Thantawi Ishak said sanctions or punishment would be discussed by the syariah council, police and the Muslim Scholars' Council.

But many women argue that punishment is a matter for God to determine. "The police can do checks but we have to answer to God if we don't conform. It is a matter between God and ourselves, so only God can punish us," said 26-year-old Devi, a human-rights activist.