Iraqis burn an effigy of Pope Benedict XVI during a demonstration, in Basra, Iraq, earlier today. The demonstration was against his speech last week in Germany, particularly his quoting of a medieval text that characterized some of the teachings of Islam's founder as "evil and inhuman."

VATICAN CITY — Pope Benedict XVI said Sunday that he is "deeply sorry" his remarks on Islam and violence offended Muslims, but the unusual expression of papal regret drew a mixed reaction from Islamic leaders as the Vatican worried about a backlash of violence.

Some Muslim leaders accepted the statement. Others said it wasn't enough, but urged Muslims to avoid violence after attacks on churches in Palestinian areas and the slaying of a nun in Somalia.

Benedict said he regretted causing offense with his speech last week in Germany, particularly his quoting of a medieval text that characterized some of the teachings of Islam's founder as "evil and inhuman" and referred to spreading Islam "by the sword."

He said those words did not reflect his own opinions.

"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 said during his weekly Sunday appearance before pilgrims.

It was an unusual step for a leader of the Roman Catholic Church. Benedict's predecessor, Pope John Paul II, issued a number of apologies during his papacy, but they dealt with abuses and other missteps by the church in the past rather than errors on his own part.

Vatican officials had earlier sought to placate spreading Muslim anger by saying Benedict held Islam in high esteem and stressed that the central thrust of his speech was to condemn the use of any religious motivation for violence, whatever the religion.

While Benedict expressed regret his speech caused hurt, he did not retract what he said or say he was sorry he uttered what proved to be explosive words.

Anger was still intense in Muslim lands.

Two churches were set on fire in the West Bank, raising to at least seven the number of church attacks in Palestinian areas over the weekend blamed on outrage sparked by the speech.

There was also concern that the furor was behind the shooting death of an Italian missionary nun at the hospital where she worked for years in the Horn of Africa nation of Somalia. The killing came just hours after a Somali cleric condemned the pope's speech.

"Let's hope that it will be an isolated fact," the Rev. Federico Lombardi, Vatican spokesman, was quoted as saying by the Italian news agency ANSA.

He said the Vatican was "following with concern the consequences of this wave of hate, hoping that it does not lead to grave consequences for the church in the world."

Police across Italy were ordered to step up security out of concern that the anger could cause Roman Catholic sites to become terrorist targets. Police outside the pope's summer palace confiscated metal-tipped umbrellas and bottles of liquids from faithful.