Eight Orthodox Christian leaders, dignitaries from other faiths, politicians and thousands of others on Sunday celebrated the anniversary of the Edict of Milan, which established toleration for Christianity in the Roman Empire 1,700 years ago.
Roman Catholic Pope Francis was not present at the liturgy in the Serbian city of Nis, his absence reflecting centuries-old divisions between the two main Christian denominations, despite moves by both towards reconciliation and dialogue.
Instead, the Catholic Church marked the same anniversary at a mass served in Nis last month by papal envoy Angelo Scola, the Cardinal of Milan. The city of Nis, 200 km (125 miles) south of Belgrade, was selected as the venue for the celebration because the emperor Constantine the Great, who proclaimed religious tolerance, was born in the then Roman city of Naissus in 272.
Ecumenical Patriarch Bartholomew was flanked by patriarchs Theophilos of Jerusalem, Kiril of Russia, Irinej of Serbia, and their counterparts from Albania, Cyprus, Poland, Slovakia and other smaller Orthodox churches, as he called in a sermon for more religious freedom and reconciliation.
"Many Christians are being persecuted these days in the Middle East, in Syria, Egypt, Iraq and Nigeria and other places, only because of the word of God and the testimony of Jesus," he said.
"They cherish everyone and are persecuted by all ... they live in good (faith) and are being persecuted as villains," Bartholomew said. He called for the release of Syriac Orthodox and Greek Orthodox Archbishops Yohanna Ibrahim and Paul Yazigi, abducted in April during fighting in the city of Aleppo.
The Syrian government has blamed rebel groups, who deny it. The celebration in Nis underscored the close ties between the Serbian Orthodox Church and its much larger Russian counterpart.
Russia is a traditional ally of Serbia, and the Kremlin has backed Serbia's refusal to recognize Kosovo, its former southern province populated mainly by ethnic Albanians, which declared independence in 2008. About 90 % of Serbians are Orthodox and they cherish Kosovo as the cradle of their medieval civilisation.
Serbia has been keen to remain Moscow's strategic ally in the Balkans, but also wants to join the European Union and is expected to stat membership talks in January.