CAIRO (AP) -- Two Coptic Christian boys have been put in juvenile detention after locals accused them of urinating on pages of the Islamic holy book, an Islamic cleric and prosecutors said Wednesday, in the latest in a series of legal cases in Egypt against alleged contempt of religion.

Accusations of insulting Islam have increased in Egypt -- particularly against Christians -- since last month's fury over an anti-Islam film produced in the United States. Such cases occurred in the past, but the flurry to prosecute in recent weeks has raised concerns over freedom of speech and over the power of ultraconservative Islamists in the country.

The new case is a rare instance of minors being accused. The boys, ages 9 and 10, were detained Tuesday in a southern town, to be held for 15 days while prosecutors investigate the accusations.

There have been 17 cases of alleged contempt of religion filed since the January 2011 revolution, including at least five in recent weeks, according to the Egyptian Initiative for Personal Rights. A female Coptic teacher in another southern town was also summoned for interrogation last week and detained for a night after her students accused her of speaking offensively of the Prophet Muhammad in class. The teacher was released from detention, but prosecutors are still investigating her, human rights activists said.

Another Coptic Christian, Alber Saber, is facing trial for posting material on his Facebook page deemed offensive of religion. He was first detained after neighbors complained he had posted the anti-Islam film, but investigators didn't find it. Nonetheless, within days he was put on trial on charges of contempt of religion. His trial began last week.

In a rare case of prosecuting an offender of Christianity, an Islamic preacher is on trial for tearing up and burning a copy of the Bible during protests last month against the film.

Charges of contempt for religion in Egypt carry a potential maximum sentence of five years in prison. Since the film, there have been calls by leaders of some Muslim nations, including Egypt, for international laws criminalizing insults to religion.

The incident with the two boys took place in the village of Ezbet Marco in the southern province of Beni Suef. Sheik Gamal Shamardal, a Muslim cleric and the local leader of a hardline Islamist group, said residents saw the boys bring pages of the Quran behind a local mosque and urinate on them. Police arrested the boys and a crowd of angry residents gathered outside the police station. Fearing violence, security forces have surrounded the village and the boys were taken to a juvenile detention facility.

Police officials confirmed that the complaint was made and said they were investigating to determine what happened. Local security chief Attiya Mazrou told The Associated Press the boys were caught with the tarnished pages of the Quran with them, but no one saw them urinate it.

"They could have found them that way. We don't know. No one saw them do it," he said. The boys are to appear before prosecutors again Sunday.

In a sign of the broader tensions that surround such cases and the increasing powers of the Islamists, Shamardal insisted the two boys could not have acted alone and said they must remain in custody until they confess who incited them. That was the only way to calm offended Muslims, he said.

"An apology is not acceptable," said Shamardal, head of the local branch of Gamaa Islamiya, which was once Egypt's largest militant group but has since renounced violence. He speculated over a wider conspiracy behind the incident -- ranging from the local priest to Coptic Christians living abroad.

The priest, he said, refused to discipline the children when told of the incident, forcing the residents to turn to the authorities. "He just dismissed it as children's play," Shamardal said. "But this feels like it was arranged" to incite religious anger.

"There was a lot of anger particularly with the circumstances the country is going through after the film," he said. "It was like spilling oil on fire."

Radical Islamists were hunted by security or imprisoned under the previous regime of former President Hosni Mubarak. After Mubarak's ouster in Feb. 2011, the groups rose to prominence, rallying popular sympathy and operating openly for the first time. Many of their leaders were released from prison after newly elected President Mohammed Morsi came to power.

Rights activists have warned that the rise of court cases using contempt of religion as a charge threatened to restrain freedom of expression. The charges are vague and mean anything can be deemed offensive, said Ishak Ibrahim, a researcher with EIPR who monitors religious freedom cases in Egypt.

Ibrahim said the boys have denied the charges.

"This is a very serious development and is an attack on freedom of expression," Ibrahim said. The writing of Egypt's constitution is taking place in the backdrop of this furious debate over what constitutes freedom of expression and how much does Islamic law feature in the charter.

The cases also are reminiscent of blasphemy laws in Pakistan, where rights activists say Islamists increasingly use blasphemy accusations against Christians and other religious minorities. Earlier this year, a young Christian girl in Islamabad was detained after she was alleged to have desecrated the Quran, but since then a Muslim cleric has been accused of fabricating the evidence against her. She has been freed on bail.

On his Twitter account, Ibrahim criticized Egypt's Islamic groups for focusing on cases of contempt of religion, while the country is boiling with economic difficulties, calls for better wages and distribution of wealth and dwindling resources.

"The rise in cases of religious contempt shows that some want to divert people's attention from demanding their rights, and keep them busy with other issues," Ibrahim wrote. "The Islamic trend has nothing to offer in terms of realizing social justice and is seeking to create issues to keep people from criticizing them."

Amr Ezzat, a columnist in the Egypt Independent newspaper, warned that the cases are opening the gates "of sectarian hell."

Going after such speech cases "is frivolous and would turn the state, police and judiciary into disciplinary watchdogs with no other responsibilities but to ensure that everyone engaging in dialogue is doing so respectably," he wrote Wednesday.