The statement said Constantinople had no right to revoke the ex-communications of Ukrainians by Moscow | Yuri Kadobnov/AFP via Getty Images Russian Orthodox Church breaks with Constantinople The move stands to become the gravest split among Christians in nearly a millennium.

The Russian Orthodox Church on Monday angrily broke all ties with the Holy Synod of the Patriarchate of Constantinople, the worldwide leadership of Orthodox Christianity, in response to a decision last week granting independence to the Ukrainian Orthodox Church.

The move by the Russian Orthodox Church, which counts nearly half of all Orthodox believers among its membership, stands to become the gravest split among Christians in nearly a millennium, since the Great Schism of 1054 that divided Eastern Orthodoxy from Catholicism.

"The members of the Holy Synod declared it impossible to continue their stay in the Eucharistic communion with the Patriarchate of Constantinople," the Russian Orthodox Church said in a statement after a meeting of leaders in Minsk, Belarus.

The pursuit of independence, or "autocephaly" in canonical terms, by the Ukrainian church has served as an contentious, emotional, and high-stakes proxy for the ongoing military struggle between Russia and Ukraine. In the decision last week, Constantinople took several steps toward independence including the reinstatement of priests, bishops and church members who had been excommunicated by Moscow.

Moscow has controlled the Ukrainian church for 332 years by authority of a synodal letter issued in 1686. Last week's decision revoked that letter.

The decision last week, which was announced by the Ecumenical Patriarch Bartholomew, the archbishop of Constantinople-New Rome and worldwide leader of Orthodox Christians Constantinople, not only granted independence to the Ukrainian church but also reinstated priests, bishops and church members who had been excommunicated by Moscow.

In a lengthy statement accusing Constantinople of acting illegally, the Russian Orthodox Church insisted that there is no justification for overturning several long-standing decisions that had affirmed Moscow's control over the Ukrainian church.

"How is it possible to cancel the decision that has been in effect for three centuries?" the Russian church asked in its statement.

The statement also insisted that Constantinople has no right to revoke the excommunications of Ukrainians by Moscow, including the leader of the Ukrainian church, Patriarch Filaret, who was effectively accused by Moscow of treason.

"Despite repeated calls for repentance, after the deprivation of his hierarchal rank, Filaret Denisenko continued his schismatic activity," the Russian church stated, adding: “Until the Patriarchate of Constantinople refuses to make anti-canonical decisions for all clergymen of the Russian Orthodox Church, it is impossible to serve the clergy of the Constantinople Church."