The Russian Orthodox Church Friday cut "diplomatic ties" with Bartholomew I, the Istanbul-based spiritual leader of the world's Orthodox Christians, accusing him of encroaching on its religious territory in Ukraine.

As Ecumenical Patriarch, Bartholomew I is expected to rule in the coming months on a Ukrainian appeal to cut spiritual ties with Moscow amid a simmering military conflict in the east of the former Soviet country.

Ahead of the decision, he sent two representatives to Ukraine this month, sparking fury in Russia.

The ruling body of the Russian Orthodox Church decided to downgrade ties with its Istanbul-based rival at an emergency meeting Friday.

"The Ecumenical Patriarchate of Constantinople has intruded on the canonical territory of the Moscow Patriarchate by sending its exarchs to Kiev," Metropolitan Hilarion, head of the Russian Church's foreign relations department, said at Moscow's Danilov Monastery.

He spoke after the ruling body of the Russian Orthodox Church, known as the Holy Synod, decided to cut what Metropolitan Hilarion described as "diplomatic ties" with the Istanbul-based rival.

According to the Holy Synod's decision, the Russian Orthodox Church will no longer conduct joint services with the Patriarchate of Constantinople and Patriarch Kirill will stop mentioning Bartholomew I in his prayers.

The Russian Orthodox Church will no longer take part in Episcopal Assemblies or any commissions or other structures chaired by representatives of Bartholomew I, said a statement released following the meeting.

If the Istanbul-based rival continues its "anti-canonical activities" the bonds will be severed completely, the statement added.

"The full responsibility for the tragic consequences of this schism will rest with Patriarch Batholomew I and bishops who support him," the statement said.

Russian Orthodox Patriarch Kirill, who is seen as a strong ally of President Vladimir Putin, wants to prevent pro-Western Ukraine from getting an independent church.

Such a move would be seen as a huge blow to Russia's spiritual authority in the Orthodox world.

The Orthodox church in Ukraine is split between a branch whose clerics pledge loyalty to Moscow and one that is overseen by the unrecognised Kiev-based Patriarch Filaret.

The split has deepened following the Russian annexation of Crimea and the outbreak of a separatist uprising in Ukraine's east in 2014.

Bartholomew I, known as Archbishop of Constantinople, New Rome and Ecumenical Patriarch, is regarded as the "first among equals" of the world's estimated 300 million Orthodox Christian believers.

While Constantinople is the oldest Orthodox Church, Moscow is currently the most powerful with the largest number of worshippers.