By Jan Repa
BBC Europe analyst
A branch of the Russian Orthodox Church - whose members fled abroad to escape the Bolshevik Revolution - has reunited with the main body of the Church at a ceremony in Moscow.
The Christ the Saviour Cathedral is a symbol of religious rebirth
The reconciliation has been strongly supported by President Vladimir Putin, who attended the televised ceremony.
Leaders of the New York-based Russian Orthodox Church Abroad flew into Moscow for the historic reunification.
At the ceremony on Thursday the Patriarch of Moscow, Alexy II, joined the leader of the Russian Orthodox Church Abroad, Metropolitan Lavry, in celebrating Mass at the Christ the Saviour Cathedral. It was blown up by the Soviet dictator Joseph Stalin, and rebuilt after the collapse of communism.
On Saturday, the two will jointly consecrate a new church on a site in southern Moscow, where the Soviet secret police shot thousands of Orthodox priests.
The Russian Orthodox Church Abroad owes its origin to the civil war - which followed the Russian Revolution of 1917 and ended with the victory of the militantly atheist Bolsheviks over the monarchist Whites.
Exiled bishops and clerics proclaimed the Russian Orthodox Church Abroad at a meeting in Serbia in 1922 - later relocating to New York.
In 1927, it broke off relations with the Russian Orthodox hierarchy in Moscow - saying it had fallen under Bolshevik control.
Mr Putin visited the Mt Athos monastery in Greece in 2005
Ruthlessly persecuted by the Soviet regime, the Russian Orthodox Church has recovered some of its old influence since the break-up of the Soviet Union in 1991.
Although church attendance remains relatively low, former Soviet functionaries like President Putin and his predecessor, the late President Boris Yeltsin, have emphasised their new-found status as Orthodox believers and have made a point of being seen at major religious festivals.
Mr Putin, in particular, has tried to involve the Russian Orthodox Church in the task of reviving a sense of Russian patriotism and "great power" consciousness. Paradoxically, this includes rehabilitating certain aspects of the Soviet past - Mr Putin himself describing the break-up of the Soviet Union as a "tragedy".
Historically, the Russian Orthodox Church's connections with the Russian state were strong and close. It was a mainstay of the tsarist regime and a champion of Russian cultural exceptionalism.
Ranked fifth in order of seniority by the other Orthodox Churches - after Constantinople (Istanbul), Alexandria, Antioch and Jerusalem - it has traditionally striven to assume first position.
In 1981, the Russian Orthodox Church Abroad proclaimed Russia's last Tsar, Nicholas II, and his family - all shot by the Bolsheviks in 1918 - as saints. Seven years ago, the Orthodox Church in Russia did the same.
Nevertheless, some members of the Russian Orthodox Church Abroad remain unhappy about this week's reunion - and have threatened to break away.
A spokesman for the Russian Orthodox Church Abroad, Archpriest Alexander Lebedev, is quoted by the Russian Interfax news agency as stressing his Church's devotion to "Russianness" - and suggesting it was uneasy about the Moscow Patriarchate's ecumenical contacts with other, non-Orthodox, Christians - notably its membership of the World Council of Churches.
But he accepted that its membership would continue "for some time to come" - in order to stop the Patriarchate of Constantinople stepping into its place.