The masked woman nervously approaches her target, shuffles into position and then unleashes a flurry of lashes -- proving herself as the newest member of the first female flogging squad in Indonesia's Aceh province.

The new recruit initially needed some coaxing to punish the offender -- an unmarried woman caught in a hotel room with a man.

Such behaviour constitutes a morality crime in Aceh, the only region in the world's biggest Muslim-majority nation that imposes Islamic law -- known as Sharia. Those found guilty of breaches are often publicly whipped with a rattan cane.

But despite her reticence, she persevered and delivered her first flogging.

"I think she did a good job. Her technique was nice," Banda Aceh Sharia police chief investigator Zakwan, who uses one name, told AFP.

The controversial punishment enrages rights activists and generates heated media debate, as well as amongst politicians.

Indonesia's president has issued a call for the public floggings to stop but he has little say over what happens in Aceh, a deeply conservative region on Sumatra island.

Unlike the rest of the nation, Aceh follows religious law as part of a 2005 autonomy deal agreed with the central government that ended a decades-long separatist insurgency.

Here, public whipping remains a common punishment for scores of offenders for a range of charges including gambling, adultery, drinking alcohol, and having gay or pre-marital sex.