Two Indonesian women have been publicly whipped nearly 100 times each for selling sex workers' services online, an official in the country's conservative Aceh province said on Tuesday.

Aceh, at the tip of Sumatra, is the only region in Muslim-majority Indonesia to impose Islamic sharia law, which allows flogging for a range of offences including prostitution, gambling, adultery, drinking alcohol, and gay sex.

The punishment was handed down on Monday in Langsa city where dozens gathered to watch the pair get lashed, despite bans on crowds over coronavirus fears.

Neither of the women wore disposable face masks, unlike in some other recent whippings.

The two hijab-wearing suspects were arrested in March along with five sex workers, who could also face a flogging if found guilty of violating Islamic law, said Aji Asmanuddin, head of Langsa's Islamic sharia agency.

"They were punished for violating sharia by advertising (sex) through the internet," Asmanuddin said.

Officials were struggling to crack down on the area's booming online sex trade, he added.

"This is the first (pimping) case in Langsa although we believe there are many of them out there," Asmanuddin said.

"We just don't have the necessary tools to monitor them online."

Rights groups have slammed public caning as cruel, and Indonesia's President Joko Widodo has called for it to end.

But the practice has wide support among Aceh's mostly Muslim population. -