Vatican City - The Muslim world's scathing reaction to Pope Benedict's comments on Islam is the biggest challenge to face the pontiff yet and raises concerns over his security, diplomatic and Church sources said on Friday.
"My personal reaction was: 'This is a striking statement. Was it a rare slip-up?'" one source said about the pope's speech in Germany last Tuesday.
"One has to wonder why the pope, who is normally so careful about what he says or writes, and has a reputation for extreme care, did not realize the reaction that this could cause," the source added.
In his speech at the University of Regensburg, Benedict quoted criticism of Islam and the Prophet Mohammed by 14th century Byzantine Emperor Manuel II Palaeologus, who wrote that everything Mohammed brought was evil and inhuman, "such as his command to spread by the sword the faith he preached".
Benedict repeatedly quoted Manuel's argument that spreading the faith through violence is unreasonable, adding: "Violence is incompatible with the nature of God and the nature of the soul."
"I was quite surprised (by the speech)," one diplomat said. "He has put himself in a tough spot and it will be interesting to see what he does next."
A growing chorus of Muslim leaders have called on the pope to apologize. Muslim scholars say his comments show little understanding of Islam and some say Islamic countries should threaten to break off relations with the Vatican.
One high-ranking Church source also also expressed fears for the pope's safety.
"While I think the controversy will go away, it has done damage and if I were a security expert I'd be worried," he said.
At least one Muslim leader, Syed Ahmed Bukhari, the chief cleric of New Delhi's historic Jama Masjid, India's largest mosque, extolled Muslims to "respond in a manner which forces the pope to apologize." He did not elaborate.
Professor or pope?
The Church source said the pope, who for years was a professor of theology in his native Germany, had perhaps made a mistake by mixing up his past and present roles.
"The question is should he, as pope, be giving very complex academic lectures and how far is he going to risk getting himself into trouble by doing so?" he said.
"What one can say as an academic is one thing and what a pope can say is another," the source added.
But another diplomatic source praised the pope for "calling a spade a spade."
"I see this as a wake up call for Christians. It will be interesting to see what the next step will be, but I don't think he has to apologize for anything, nor do I think he will," the diplomatic source said.
Some sources said they feared the controversy could affect the pope's plans to visit Turkey in November for a major meeting with Orthodox leaders. There have already been some calls in Turkey for the trip to be cancelled.
A Vatican statement on Tuesday said it was not the pope's intention to offend the sensitivity of the Muslim faithful.
Cardinal Paul Poupard, head of the Vatican's department for inter-religious dialogue, invited "Muslim friends of good will" to read the entire text of the pope's lecture.
He told Corriere della Sera newspaper it should be seen as an offer to discuss "humanity's religious cultures and the great role Islam has in them."