From Russia to Ethiopia, Eastern Rite and many Orthodox Christians who follow the Julian calendar are celebrating Christmas today.
In Moscow, Patriarch Kirill celebrated a midnight Mass at Christ the Savior Cathedral.
It was Kirill's first Christmas Mass as leader of the Russian Orthodox Church.
President Dmitry Medvedev was among some 4,000 people attending the service, which was broadcast on national television.
"Christmas is a great celebration for all Orthodox Christians," churchgoer Tamara told Reuters. "It's renewal. It's good -- beauty and hope for a bright future."
After the service, Medvedev gave the patriarch a modern, hand-written New Testament.
Russian President Dmitry Medvedev and wife Svetlana among children at a Christmas service in Moscow
Kirill presented Medvedev with a four-volume collection of the works of Russian writers and poets of the 14th to 20th centuries.
Prime Minister Vladimir Putin was in Kostroma, on the banks of the Volga River to celebrate Christmas mass.
During Soviet times thousands of churches were demolished, including Christ the Savior Cathedral, which was rebuilt in the late 1990s.
Orthodox Christmas became a public holiday in Russia following the collapse of the Soviet Union in 1991.
Russia's Interfax news agency quoted the Moscow Patriarchate as saying there are some 30,000 Russian Orthodox churches around the world that will be marking Christmas on January 7 as well as other churches that still use the Julian calendar.
Under the Gregorian calendar, used by other, predominantly Western churches and commonly in secular life, Christmas falls on December 25.Around The World
Today's Christmas celebrations were marked by tensions in some parts of the world.
In the Balkans, Serbian President Boris Tadic celebrated
Orthodox Christmas in Kosovo, which seceded from Serbia two years ago.
Tadic spent the night with monks, lighting candles, burning yule logs, and attending midnight Mass at the Serbian Orthodox medieval monastery of Visoki Decani.
Flanked by Bishop Teodosije of the monastery, Tadic pledged to come to the monastery "every year," adding that the sacred place represented "a guarantee of our identity."
Serbian President Boris Tadic (left) with Bishop Teodosije outside the Visoki Decani Monastery on Christmas eve
About 100 ethnic Albanians protested the visit, marching toward the 14th-century monastery, waving Albanian flags, and chanting anti-Serb slogans.
The protesters were kept away from the monastery by NATO peacekeepers.
The visit also drew strong criticism from Kosovo's authorities. Xhavit Beqiri, the spokesman for Kosovo's president, said it "does not help the relaxation of the relations between Serbia and Kosovo."
But Tadic said the purpose of his visit was to call for peace in the Balkans.
In the West Bank town of Bethlehem, the traditional birthplace of Jesus, hundreds of pilgrims watched a procession led by the Greek Orthodox Patriarch of Jerusalem, Theophilos III.
Palestinian riot police escorted the cleric to the Church of the Nativity to the sound of protests by Palestinians accusing Theophilos of selling land to Israelis.
Celebrations turned violent in southern Egypt, where angry Christian Copts clashed with police today.
The violence came after unidentified gunmen opened fire on a crowd leaving a church after Christmas Mass in the southern town of Nagaa Hammadi, killing six Copts and a Muslim policeman.
Authorities said the attack was suspected to be retaliation for the rape of a Muslim girl by a Christian man in the town in November.
According to government figures, Christians make up approximately 10 percent of Egypt's population, though many Christians say they believe the real figure is higher.compiled from agency reports