Islamic authorities in the Nigerian city of Bauchi have reportedly launched a crackdown on sex workers identified by the Red Cross in a census.
The BBC's Shehu Saulawa in Bauchi says that the local Sharia commission has begun rounding the women up.
But a commissioner said no arrests had been made and authorities were merely "supervising" against illicit acts.
The Red Cross carried out the census amid efforts to tackle the spread of HIV in the north-eastern state.
Muslim majority Bauchi is governed by the Islamic Sharia law.
After the census had identified 320 women, the local Sharia commission ordered that they be rounded up, our correspondent reports from Bauchi.
He says the Sharia commission seems to have been prompted to act by the perception that it was unable to enforce a ban on commercial sex workers in the state.
The Red Cross identified sex workers amid efforts to tackle HIV
The Sharia commission normally liaises with the police, he says, but this time they acted directly, using their own security force to raid hotels housing an unknown number of sex workers.
Mustapha Babe, a member of the Sharia commission in Bauchi, denied that any women had been detained, saying the committee responsible for law and order was only supervising parts of the city.
"In every nook and corner and cranny, illegal acts were being committed contrary to Sharia law," he said.
"As a result of this, we sent them to supervise the areas where something has happened."
Between 75 and 100 of the 320 women have so far tested positive for HIV.
Several of Nigeria's Muslim majority northern states introduced Sharia law starting in 2000, despite opposition from Christians, sparking clashes and riots between rival groups.
The new laws reintroduced some of the harsher Islamic penalties which had been removed under colonial rule.