Benedict flew by helicopter to the Adriatic port of Bari, considered a "bridge" between East and West that is home to the relics of St. Nicholas of Myra, a 4th-century saint who is one of the most popular in both the Roman Catholic and Orthodox churches.
The trip was Benedict's first outside Rome since being elected the 265th leader of the Roman Catholic Church on April 19 and, though brief, showed he was following in the much-traveled footsteps of his predecessor, Pope John Paul II. After the 3 1-2 hour visit, he departed by helicopter for the Vatican.
Benedict referred to Bari as a "land of meeting and dialogue" with the Orthodox in his homily at a Mass that closed a national religious conference.
"I want to repeat my willingness to assume as a fundamental commitment working to reconstitute the full and visible unity of all the followers of Christ, with all my energy," he said to applause from the estimated 200,000 people at the Mass.
Words aren't enough, he said, adding that "concrete gestures" were needed even from ordinary Catholics to reach out toward the Orthodox.
"I also ask all of you to decisively take the path of spiritual ecumenism, which in prayer will open the door to the Holy Spirit who alone can create unity," he said.
Benedict has said previously that reaching out to the Orthodox and other Christians would be a priority of his papacy, and his call to ordinary Catholics to take the charge as well built on that agenda.
The most-traveled pope in history, John Paul made 104 foreign pilgrimages and 146 pastoral visits in Italy during his 26-year papacy. John Paul visited Bari in 1984.
Benedict, 78, has said he is looking forward to attending the World Youth Day celebrations in Cologne, in his native Germany, this August — a trip John Paul had hoped to make himself.
Polish bishops have said they also want Benedict to visit the late pope's homeland.
Wearing his bishop's miter and white vestments, Benedict blessed the faithful, many of whom waved the Vatican's yellow and white flags or white baseball caps handed out by organizers to shield them from the sun.
Swiss Guards in full regalia stood at attention near the altar. It was the first time in recent history that uniformed Swiss Guards accompanied the pope on a trip inside Italy, but would continue, Vatican officials said.
Security in the city was tight, with the town center and seaside boulevard leading to the Mass site closed to regular traffic. Hundreds of police patrolled the streets, coastal waters were closed to private vessels and the Italian navy ship San Giusto was anchored nearby, officials said.
In his greetings at the start of the Mass, Archbishop Francesco Cacucci of Bari referred to the city's Orthodox ties, saying the arrival of St. Nicholas' bones in 1057 "built a bridge between the East and West that neither time nor divisions have ever demolished."
"Even in these days, many brothers of the eastern churches have been united with us, encouraging us to continue with renewed commitment and enthusiasm on the path of prayer and ecumenical dialogue," the archbishop said.
In a bid to improve relations, the Vatican's top ecumenical official, Cardinal Walter Kasper, proposed this week at the Bari conference to hold a synod, or meeting of Catholic and Orthodox bishops, news reports said.
Father Vladimir Kuciumov, rector of the Russian Orthodox Church in Bari, said Benedict had already made a good start toward improving relations with the Orthodox in some of his inaugural homilies and speeches.
"We hope for the best," he said in a telephone interview Sunday. "We still have to see, but there is hope to improve our relations."
The Italian media had been speculating that Benedict would use his first pilgrimage in Italy to weigh in on a pressing national issue: upcoming referendums on voiding parts of a new law that restricts assisted fertility treatment in Italy. Italian bishops have urged voters to stay home so the referendums fail to reach quorum.
It seemed more likely though, that Benedict would use an audience with the Italian Bishops' Conference on Monday to make any reference to the issue.