"The divisions which exist among Christians are a scandal to the world and an obstacle to the proclamation of the gospel," Benedict said in his homily at the colorful service in the incense-filled Church of St. George.

Benedict's service with Patriarch Bartholomew, spiritual leader of the world's 250 million Orthodox Christians, was held on the feast of St. Andrew the apostle, who is said to have preached in what is now Istanbul after Christ's death.

Benedict's visit has been marked by the tightest security ever seen for a foreign visitor. A few dozen supporters of a nationalist Islamist party protested against the Pope outside Istanbul University under heavy police guard.

By Public Radio of Armenia