Pope Benedict XVI and the spiritual leader of the world's Orthodox Christians held a solemn prayer service together Thursday in the Church of Saint George in Istanbul. During the joint ceremony they re-committed their churches to the quest for full unity. For VOA, Sabina Castelfranco reports from Istanbul.

On the day Christians mark the feast day of Saint Andrew the apostle, Pope Benedict and Patriarch Bartholomew I held a joint ceremony in the Church of Saint George in Istanbul. The Orthodox Liturgy was nearly three-hours long and full of symbolism.

Pope Benedict XVI, left, and Ecumenical Patriarch Bartholomew I at Ecumenical Patriarchate in Istanbul, 30 Nov 2006

During the ceremony the leaders of the world's Catholics and Orthodox pledged to continue all efforts towards full Christian unity between their churches. The Western and Eastern branches of Christianity split in the Great Schism of 1054 over differences on theology and papal authority.

"'The divisions which exist among Christians are a scandal to the world and an obstacle to the proclamation of the Gospel," said the pope.

Inside the church, the pope also urged "all world leaders to respect religious freedom as a fundamental human right."

The pope also took the opportunity to reiterate the importance of Europe's Christian roots.

"We are called together with all other Christian communities to renew Europe's awareness of its Christian roots, traditions and values, giving them new vitality," he said.

At the end of the liturgy, the pope and the patriarch joined hands and greeted a crowd from a balcony. In a joint statement, the pope and patriarch stressed the need to "preserve Christian roots" in European culture while remaining "open to other religions and their cultural contributions."

While the ceremony was under way, outside Istanbul University, some 100 nationalists protested against Pope Benedict's visit and called on him to stay away from Aya Sofya, which was once Christianity's largest church and is now a museum.

Amid heavy police presence supporters of the right-wing Grand Unity Party waved banners displaying "Pope get out of Turkey" and chanted "Aya Sofya is Turkish and will remain Turkish."

The pope was to visit the 1500-year-old Aya Sofia and the Blue Mosque Thursday evening. His tour of the Blue Mosque in Istanbul will be only the second papal visit in history to a Muslim place of worship.