Patriarch Kirill of Moscow and All Russia (R) and Ecumenical Orthodox Patriarch Bartholomew I hold a liturgy to mark 1,700 years since the Edict of Milan, when Roman emperor Constantine issued instructions to end the persecution of Christians, in the southern Serbian city of Nis October 6, 2013. REUTERS/Marko Djurica

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.