(CNN) A schism has erupted within the eastern Orthodox church, threatening bitter divisions for its roughly 300 million followers.
Stemming from the deadly war in eastern Ukraine, a power struggle has emerged that pits the Russian Orthodox Church headquartered in Moscow against Bartholomew I of Constantinople, a 78-year-old, ethnic Greek cleric living in Istanbul.
The conflict is roiling a branch of Christianity that prides itself on preserving rituals and traditions that originated during the Byzantine Empire more than a thousand years ago.
On Monday, the Russian Orthodox Church -- which is lavishly funded and enjoys close political ties with Russian president Vladimir Putin -- announced it was cutting ties with Bartholomew.
Bartholomew infuriated his Russian Orthodox counterparts last week when he announced he would recognize the establishment of an independent Orthodox Church in Ukraine, revoking a centuries-old agreement -- dating back to 1686 -- which granted the Patriarch in Moscow authority over churches in the country.
In its statement, the Moscow Patriarchate -- the Russian Orthodox Church's clerical leadership -- said it would no longer accept clergy from its counterpart in Istanbul, the Constantinople Patriarchate, and announced its followers could no longer attend services in churches that follow Bartholomew.
But while the Christian population in mostly-Muslim Turkey has dwindled to just a few thousand over the last century, the world's Orthodox Christians call Ecumenical Patriarch Bartholomew "first among equals," and many view him as the spiritual and symbolic leader of their faith.
Loosely put, Bartholomew is the Orthodox equivalent of the Pope, though the Catholic Church has a stricter hierarchical structure than its eastern counterpart.
"This is something historic that I think will result in a schism," says Rev. Alexander Laschuk, a Ukrainian Catholic priest who teaches canon law at the University of Toronto.
"The question is -- is this something short or something that will last centuries?"
The rift is already drawing comparisons to the East-West Schism of 1054, which split Catholic Christians from eastern Orthodox Christians, and England's King Henry VIII's 1531 decision to break away from the authority of the Pope in Rome, a move which led to the foundation of a Protestant church in England.
"Over the centuries there have been a number of these splits, which usually turn out to be power struggles between different individuals," says Robert Brinkley, an expert on the former Soviet Union at the London-based think tank Chatham House.
Bartholomew's decision to recognize an independent Ukrainian Orthodox Church delighted Ukrainian president Petro Poroshenko, whose government is battling Russian-backed separatists in the east of the country, and demanding the return of Crimea, which Russia annexed in 2014.
"The empire is losing one of the last levers of influence over its former colony," Poroshenko said.
Political and religious circles in Moscow condemned the move.
Last Friday, Russian President Vladimir Putin led a security council meeting focused on Bartholomew's decision. Three days later, the Moscow Patriarchate severed ties with the Greek religious leader.
Accusing the Constantinople Patriarchate of "predatory actions" and an "anti-church political project," Metropolitan Hilarion Alfeyev, a spokesman for the Moscow Patriarchate, declared that Bartholomew "has now lost the right to be called the coordinating center for the Orthodox Church."
Roughly half of the world's Orthodox Christians live in Russia. Since the collapse of the Soviet Union -- which was officially atheist -- in 1991, the Russian Orthodox Church has become an important national symbol frequently and is publicly embraced by Putin.
"The Russian Orthodox Church acts as the spiritual arm of the Russian state," says Chatham House's Robert Brinkley.
"In terms of Russia trying to keep together its old empire, in particular Ukraine and Belarus, the Russian Orthodox Church has been an important instrument in seeking to do that."
The potential loss of tens of millions of Orthodox Ukrainians and thousands of Ukrainian church parishes would be a serious blow to the prestige of the Russian Orthodox Church and by extension, the Kremlin.
"We're talking about power, we're not talking about people. We're talking about territory and power and authority," says Laschuk.
In his announcement last week, Bartholomew appealed to all sides to "avoid appropriation of churches, monasteries and other properties, as well as every other act of violence and retaliation."
The power struggle between clerics in Moscow, Istanbul and Kiev has raised fears of tension boiling over at churches in Ukraine, and the rift is already being felt among Orthodox priests as far away as the US.
"This is a blow to Orthodox unity," said Archpriest Victor Potapov, rector of St John the Baptist Russian Orthodox Cathedral in Washington DC.
He predicts Russian Orthodox priests in the US linked to the Moscow Patriarchate will likely have to cut liturgical ties with clerics associated with Patriarch Bartholomew.
"We have a priest from the Ecumenical Patriarch who serves with us on a weekly basis," he says.
"I don't know what going to become of that."
He says that the schism is causing "a lot of heartache" in the Orthodox world.
"People are taking sides ... every single town in the US that has Orthodox clergy will be immediately affected," says Rev. John Jillions, chancellor of the Orthodox Church in America, an organization which represents some 700 hundred parishes in North America and operates independently from the Patriarchate in Moscow.
"In the short term, in a place like Ukraine there could be tussles over property and who owns what," Jillions says.
"In the long run, these kinds of divisions have occurred throughout 2000 years of Christian history."