Egypt's ruling military jailed a veteran dissident and blogger on Sunday on charges of inciting deadly clashes between soldiers and Christians this month, his sister and a fellow activist said.
Alaa Abdel Fatah, who was jailed for his activism under ousted president Hosni Mubarak's government in 2006, was remanded in custody for 15 days, said his sister Mona Seif, who is also a leading opponent of military trials.
The prosecutor may choose to formally refer him to a military court or release him.
Abdel Fatah's detention came days after US President Barack Obama called on Egypt's military to lift a state of emergency and end military trials for civilians.
Bahaa Saber, another activist who faces the same charges but was not detained, said he and Abdel Fatah were charged with inciting attacks against soldiers and participating in the October 9 clashes in Cairo.
Coptic Christians were protesting against an attack on a church when clashes broke out with soldiers outside the state television's building. Twenty-five people died in the violence, most of them Copts.
Witnesses said soldiers fired upon protesters and ran them over with armoured cars, accusations the military has denied. The military said a number of its soldiers died in the clashes but has refused to give a toll.
"We are charged with inciting attacks against soldiers and participating in them," said Saber.
Saber said he and Abdel Fatah attended the military prosecutor's summons on Sunday "convinced that the military has no right to intervene in judicial matters," and they refused to answer the prosecutor's questions.
"It was humiliating and unacceptable," he said. "This is an unjust escalation by the military. I will not be silenced nor intimidated, and I don't think people will be silent either."
The military has tried thousands of civilians since it took charge of the country after Mubarak's ouster on February 11, in trials rights groups say are unfair and result in harsh sentences.
Saber said the pair's lawyers were not allowed to see the military prosecution's evidence.
Seif said several people, including a journalist and a blogger who opposes the uprising that ousted Mubarak, had filed complaints against her brother.
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The blogger, who calls himself Ahmed Spider, posted on YouTube an interview with Abdel Fatah that he said led to the military prosecutor's charges.
The video shows Abdel Fatah at a protest saying he wanted to "cut off the military's hand" and threatening to storm the interior ministry.
Saber questioned the military's impartiality in investigating the deadly clash, given its role in the incident.
Military spokesmen were not immediately available for comment, but top generals have denied that soldiers killed any demonstrators and blamed a plot by "enemies of the people."
The military has ordered the caretaker cabinet it appointed to investigate the violence.
Earlier this month, influential Egyptian talk show host Yosri Fouda announced he had suspended his show in protest at media censorship.
Several newspaper columnists have also withheld their columns this month in a protest against what they say is military censorship.
Last Thursday, Paris-based media rights groups Reporters without Borders expressed concern at the plight of Fatah, Saber and other "cyber-activists" in Egypt.
It accused the current regime of pursuing "increasingly repressive policies towards the Internet and bloggers" and said the situation for Internet-based activists had worsened since the fall of Mubarak.
On October 22, Ayman Youssef Mansour was sentenced to three years' forced labour for having insulted Islam on Facebook, said RSF.
And on October 18, a court ordered blogger Maikel Nabil Sanad, who is serving a three-year sentence for insulting the armed forces, confined to a psychiatric clinic for 45 days after he began a hunger strike, it added.
Although the military was hailed during the uprising for not siding with Mubarak, it now faces growing discontent over its trials of civilians and suspicion that it is delaying a transition to civilian rule.
It has lashed out at critics, accusing one youth movement that spearheaded the anti-Mubarak revolt, April 6, of carrying out "foreign" plots.
The country is scheduled to start parliamentary elections on November 28, followed by presidential polls sometime in 2012.