About 30 Sudanese women have been arrested for holding a protest march over a video which allegedly shows a policeman whipping a woman.
The women were detained as they tried to hand a petition to the justice ministry in Khartoum.
The authorities have said they are investigating the alleged whipping, which has been widely circulated on the YouTube website.
The BBC's James Copnall in Khartoum says flogging is a common punishment.
Those convicted of crimes ranging from selling alcohol to "indecent dressing" or adultery are sentenced to lashes by Sudan's Sharia courts.
The video purports to show Sudanese policemen whipping a woman in front of a crowd, as she kneels on the floor, crying out.
YouTube has removed some of the postings of the video but on Tuesday, it could still be easily found.
"Humiliating your women is humiliating all your people," the women shouted as they were being arrested, reports the Reuters news agency.
Some officials say the video is not genuine but Khartoum State Governor Abder Rahman al-Khidir told local TV the woman had been punished under Sharia law and a "mistake" had been made, the AFP news agency reports.
During the arrests, our correspondent was kicked to the ground and had his equipment confiscated.
Sharia, or Islamic law, has long been implemented in Khartoum but when attempts were made to introduce it countrywide in 1983, people in the south, where most people are Christian or follow traditional religions, took up arms in protest.
After a 2005 peace deal, a referendum is due in January on whether the south should secede from Africa's largest country.