UKRAINE: As Ukraine's Catholics prepare to open their headquarters in the national capital, Kiev, the Russian Orthodox Church has denounced the move as an act of aggression by the Vatican.
On Sunday, Ukraine's five million-strong Catholic Church - which for 400 years has performed Orthodox rites while recognising the authority of the Pope - will mark the transfer of their see to Kiev from the western city of Lviv.
But the decision has enraged Moscow Patriarch Alexiy II, who has called it proof of the Vatican's determination to convert Orthodox believers in Ukraine and elsewhere in the former Soviet Union.
"Without doubt these are unfriendly steps, which will cause even more tension in our relations with the Ukrainian Greek Catholic and Roman churches," Alexiy said.
"These activities cannot be justified from a historical point of view, or from the point of view of church rules and canons. The Kievan pulpit has from the first years of its existence been one of the capitals of the Russian Orthodox Church."
The latest row deals a blow to Pope Benedict's avowed intention to improve relations between the Catholic and Orthodox churches, which split in 1054.
The Ukrainian Uniate or Greek Catholic Church was established in 1596, when much of modern-day Ukraine was ruled from Poland, and allowed Orthodox priests to continue performing Byzantine rites while giving allegiance to the Vatican.
Under the Soviet regime, Uniate churches were razed or handed over to the Orthodox Church, while clergy were imprisoned or exiled, and services were performed secretly.
Only in the late 1980s was the Uniate Church again legalised, but its resurgence has irked the Orthodox Church, which counts the vast majority of Ukraine's 47 million people among its congregation.
"Persistent attempts by the Ukrainian Greek Catholics to move their see to Kiev . . . show who is the aggressor in Orthodox-Catholic relations," said Father Vsevolod Chaplin, a spokesman for the Moscow Patriarchate.