ROME — Pope Benedict XVI addressed believers from the balcony of his summer residence at Castel Gandolfo yesterday amid extraordinary security measures put in place after a weekend of anti-Christian violence across the Middle East and personal threats against the pontiff.

Pilgrims who made the trip to hear the pope speak were thoroughly searched. Swiss guards lined the walls of the papal palace outside Rome, and military police patrolled the perimeter of the normally sleepy hilltop town.

Checkpoints with metal detectors were set up on all the roads and walkways leading to the town center.

At the Vatican, plainclothes policemen mingled with the crowds of pilgrims and tourists in St. Peter’s Basilica. Italy’s interior ministry has instructed police to redouble their checks on possible Islamic extremists across the country.

After a weekend of violent protests by Muslims, in which six churches were burned in the Palestinian Arab territories and an effigy of the pope was burned in India, some feared of further attacks on Christian targets.

An Italian nun was gunned down in the Somali capital, Mogadishu, yesterday but her Italian order said they did not believe the killing was related to the controversy over the pope.

Muslims across the world protested after the pontiff quoted an obscure medieval text, citing the words of a Byzantine emperor who characterized some of the teachings of the Prophet Muhammad as “evil and inhuman.”

The Vatican explained that the Pope’s choice of quote was meant as a “clear and radical refusal of religion as a motivation for violence.” In a carefully worded apology yesterday, Pope Benedict XVI announced that the Vatican would go on a diplomatic offensive to try to calm the storm in the Islamic world.

“We have ordered the Apostolic Nuncios [the Vatican’s ambassadors] in Muslim countries to take and explain my declaration to political and religious leaders, highlighting the elements which have been ignored up to now,” he said.

“I hope that this serves to appease hearts and to clarify the true meaning of my address, which in its totality was and is an invitation to frank and sincere dialogue, with great mutual respect,” the pope added as his Angelus address drew to a close.

But it was not clear last night if the pope’s personal address had gone far enough to appease his critics. The pontiff fell short of apologizing for using the offending quote in his lecture to theology students in Bavaria. Instead, he apologized for unintentionally causing the violent reactions that followed.

And a subtle difference between the Italian words used by the pope and the English translation issued by the Vatican left his exact stance somewhat unclear. While the official Vatican translation of the pope’s words contained the word sorry, Benedict said “Sono rammaricato,” which normally translates as “I am disappointed” or “I regret.”

If the pope said he was disappointed by the reactions to his lecture, this was far from an apology. In Iran, the Apostolic Nuncio, Monsignor Angelo Mottola, was called to the foreign ministry to explain the pope’s words. The head of the Pontifical Council for Justice and Peace, Cardinal Renato Martino, defended the pope in an article in the Osservatore Romano, the Vatican’s newspaper. He wrote that the pope’s speech was a “rich and complex” lesson and that bits of it “should not be extrapolated or decontextualized.”