Munich, Germany - Pope Benedict XVI's trip to his native Bavaria had all the sentimentality of a favourite son's homecoming but his provocative equation of Islam with violence is a sting in the tail which is likely to reasonate for months.
A growing clamour of angry leaders from across the Muslim world had begun to drown out the joyous cacophany of choirs and church bells even before the papal plane had left the ground at Munich airport on Thursday for the flight back to Rome.
Turkey's top Muslim religious leader described the pontiff's remarks as hateful, prejudiced and biased, and opposed his planned visit to Turkey in November.
They "reflect the hatred in his heart. It is a statement full of enmity and grudge," said Ali Bardakoglu, the head of the state-run religious affairs directorate.
The head of the French Council for the Muslim Religion (CFCM) demanded a "clarification" from the Vatican.
"We hope that the Church will very quickly give us its opinion and clarify its position so that it does not confuse Islam, which is a revealed religion, with Islamism, which is not a religion but a politial ideology," Dalil Boubakeur told AFP by telephone.
Senior Islamic officials in Kuwait demanded an immediate apology from the pope to the Muslim world for his "calumnies against the Prophet Mohammed and Islam."
Independent Moroccan newspaper "Aujourd'hui" said the pope had "pointlessly" upset the world's Muslim population of one billion.
In what some Vatican watchers see as a watershed speech to academics on Tuesday, Benedict had portrayed Islam as a religion which endorses violence, where faith is "spread by the sword".
The speech at Regensburg University explored the historical and philosophical differences between Islam and Christianity, and the relationship between violence and faith.
The pope couched his criticism of the founder of Islam in a historical reference to a 14th century Byzantine emperor.
"He said, I quote: 'Show me just what Mohammed brought that was new and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached.'"
Benedict said "I quote" twice to clarify the phrase was not his own.
"Violence is incompatible with the nature of God and the nature of the soul," he added.
The reaction from the Muslim world to his comments has tarnished what had been a successful visit to Germany, where a more relaxed Benedict was on display to the world.
The academic, who at times has been painfully shy since succeeding the late John Paul II 17 months ago, seemed at ease amongst his compatriots.
During his public appearances he pressed the flesh with a politician's verve, kissed babies and, for this week at least, mothballed his image as a dour defender of the faith, honed by 24 years as the Vatican's doctrinal enforcer.
"On this visit, it has been great for me to see a pope who is so open and friendly," said 36-year-old teacher Angelika Huber, watching the pope's cavalcade roll through the town of Freising on Thursday with her husband and two children.
"I really think he has defied the criticism of him and shown that he is a warm person, and not some cold figure who just sits in the Vatican."
Karl Lehmann, chairman of the German bishops' conference, said the pope had shown that he performs his duties "with a simple but direct style".
However, the pope may now have to use his November visit to Turkey and its 70 million Muslims as a major bridge-building exercise.
Benedict had highlighted closer ties between Christians and Muslims, and Christians and Jews as priorities of his pontificate within days of his election in April last year.
He met both Muslim and Jewish leaders in Cologne a few months later, during his first foreign visit as pontiff.
In a few hours in Regensburg, he has undone much of the groundwork done in Cologne a year before.