CASTEL GANDOLFO, Italy (CNN) -- Pope Benedict XVI on Sunday said he was "deeply sorry" for the reaction to comments he made last week when he quoted from a 14th-century emperor regarding Muslims.

"These in fact were quotations from a medieval text, which do not in any way express my personal thought," the pope said in his regular Sunday blessing, the Angelus.

The pontiff spoke to a rain-soaked crowd at Castel Gandolfo, his summer residence outside Rome, in his first public comments since the controversy erupted last week. (Watch pope apologize as Muslims protest -- 2:02)

The pope said he hoped his remarks and the Vatican's explanation Saturday were enough 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." (Vatican statement)

The remarks came last Tuesday, when the pope spoke to professors in Germany and quoted 14th-century Byzantine emperor Manuel II Paleologus.

"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 quoted. (Full story)

Reaction from Muslims around the world was strong and swift, prompting Italian police to raise the alert level around the Vatican and Castel Gandolfo, a police spokesman said. (Watch Muslims around the world react with anger and disappointment -- 1:54)

Although measures to safeguard sensitive targets have never been relaxed, the spokesman said, "obviously, given the circumstances, the attention level has gone up."