The Russian hackers indicted by the US special prosecutor last month have spent years trying to steal the private correspondence of some of the world's most senior Orthodox Christian figures.

Key points: Associated Press has found evidence of hacking on senior figures in the Eastern Orthodox Church

Associated Press has found evidence of hacking on senior figures in the Eastern Orthodox Church Leader Bartholomew I is considering a Ukranian bid to separate from the church in Russia

Leader Bartholomew I is considering a Ukranian bid to separate from the church in Russia The hacking was by the Fancy Bears group, who were also implicated in the US presidential election hacking

AP revealed the information about the attacks as Kiev and Moscow wrestled over the religious future of Ukraine.

The targets included top aides to Ecumenical Patriarch Bartholomew I, who often is described as the first among equals of the world's Eastern Orthodox Christian leaders.

The Istanbul-based patriarch is currently mulling whether to accept a Ukrainian bid to tear that country's church from its association with Russia, a potential split fuelled by the armed conflict between Ukrainian military forces and Russia-backed separatists in eastern Ukraine.

AP's evidence comes from a hit list of 4,700 email addresses supplied last year by Secureworks, a subsidiary of Dell Technologies.

AP has been mining the data for months, uncovering how a group of Russian hackers widely known as Fancy Bear tried to break into the emails of US Democrats, defence contractors, intelligence workers, international journalists and even American military wives.

In July, as part of special counsel Robert Mueller's ongoing investigation into Russian interference in the 2016 US election, a US grand jury identified 12 Russian intelligence agents as being behind the group's hack-and-leak assault against Hillary Clinton's presidential campaign.

The targeting of high-profile religious figures demonstrates the wide net cast by the cyberspies.

Bartholomew I (R) with Ukranian President Petro Poroshenko. ( AP: Mikhail Palinchak )

Move could lead to split in Orthodox church

Patriarch Bartholomew claims the exclusive right to grant a "Tomos of Autocephaly", or full ecclesiastic independence, sought by the Ukrainians.

It would be a momentous step, splitting the world's largest Eastern Orthodox denomination and severely eroding the power and prestige of the Moscow Patriarchate, which has positioned itself as leading player within the global Orthodox community.

Bartholomew I near the Kremlin in Moscow. ( AP: Dmitry Astakhov )

Ukraine is lobbying hard for a religious divorce from Russia and some observers say the issue could be decided as soon as next month.

"If something like this will take place on their doorstep, it would be a huge blow to the claims of Moscow's transnational role," said Vasilios Makrides, a specialist in Orthodox Christianity at the University of Erfurt in Germany.

"It's something I don't think they will accept."

The Kremlin is scrambling to help Moscow's Patriarch Kirill retain his traditional role as the head of the Ukrainian Orthodox Church and "the more they know, the better it is for them", Mr Makrides said.

The Russian Orthodox Church said it had no information about the hacking and declined comment.

Russian officials referred AP to previous denials by the Kremlin that it had anything to do with Fancy Bear, despite a growing body of evidence to the contrary.

Ukrainian President Petro Poroshenko flew to Istanbul in April in an effort to convince the patriarch to agree to a split, which he has described as "a matter of our independence and our national security".

Moscow's Patriarch Kirill is flying to Turkey later this week in a last-ditch bid to prevent it.

Hilarion Alfeyev, Kirill's representative abroad, has warned that granting the Tomos could lead to the biggest Christian schism since 1054, when Catholic and Orthodox believers parted ways.

"If such a thing happens, Orthodox unity will be buried," Mr Alfeyev said.

'Kiev is Jerusalem for the Russian Orthodox people'

Mr Bartholomew, who is 78, does not use email, those church officials told AP.

But his aides do, and the Secureworks list spells out several attempts to crack their Gmail accounts.

Among them were several senior church officials called metropolitans, who are roughly equivalent to archbishops in the Catholic tradition.

Those include Bartholomew Samaras, a key confidante of the patriarch; Emmanuel Adamakis, an influential hierarch in the church; and Elpidophoros Lambriniadis, who heads a prestigious seminary on the Turkish island of Halki.

Priests and prelates do not make obvious targets for cyberespionage, but the stakes for the Kremlin are high as the decision on Tomos looms.

Granting the Ukrainian church full independence "would be that devastating to Russia", said Daniel Payne, a researcher on the board of the JM Dawson Institute of Church-State Studies at Baylor University in Texas.

"Kiev is Jerusalem for the Russian Orthodox people," Mr Payne said.

"That's where the sacred relics, monasteries, churches are … it's sacred to the people, and to Russian identity."

AP