Prominent Egyptian youth leader Ahmed Duma was arrested on Tuesday for participating in a protest, his wife told AFP, the third pro-democracy activist to be detained within a week.
Egyptian authorities have widened their crackdown on protesters since interim president Adly Mansour passed a law on November 24 that bans all unauthorised demonstrations.
"He has been arrested for participating in a violent protest outside a court. He is now being interrogated by the prosecution," Duma's wife Nurhan Hefzy said.
Duma also wrote about his arrest on his Twitter account.
"I am now in Basateen police station. I don't know what I am accused of and what is the reason for my arrest," he tweeted.
An Egyptian judicial source said Duma was being questioned for participating in a violent protest outside a Cairo court on Saturday when another prominent activist Ahmed Maher turned himself in after he was ordered arrested by the general prosecution.
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The source said that the general prosecution is also investigating a separate complaint filed against Duma and another activist Asma Mahfouz for allegedly "insulting" army chief General Abdel Fattah al-Sisi, who is seen as the real power behind the nation's interim rulers.
In June, Duma was sentenced to six months in jail for insulting ousted president Mohamed Morsi during a television broadcast as "a criminal and murderer".
He was released on July 6, three days after the army ousted Morsi.
Duma is the third pro-democracy activist to be arrested within a week after Maher and Alaa Abdel Fattah, who have been detained for taking part in unauthorised protests.
Abdel Fattah has been sent to 15 days detention. Maher was ordered free Sunday in one case after he had turned himself in at a Cairo court, but on Monday he was detained again for four days.
The new law stipulates that permission to hold gatherings can be denied if a planned protest is deemed a threat to national security.