MOSCOW - A new patriarch took charge of the Russian Orthodox Church in a ceremony Sunday to become the first leader of the world's largest Orthodox church to take office after the fall of the Soviet Union.

Patriarch Kirill, a veteran church diplomat and cautious advocate of change, became the 16th person to bear the title in a solemn ceremony at Christ the Savior Cathedral, Moscow's most opulent church and itself a symbol of the rebirth of the Orthodox faith.

The original 19th-century church was dynamited under Soviet dictator Josef Stalin in 1931, but rebuilt in the late 1990s following the collapse of the officially atheist Soviet Union.

The vast cathedral was filled with ancient chants, incense smoke and politicians holding candles early Sunday as the gray-bearded Kirill, 62, received his vestments including a black-and-gold embroidered cassock and a gold brocade miter.

The ceremony was attended by dozens of top clerics as well as President Dmitry Medvedev, Prime Minister Vladimir Putin and scores of other government officials from Russia and ex-Soviet states.

The ceremony was broadcast live on national television.

Kirill was elected Tuesday by a church council that consisted of top clerics, monks and lay electors, including government officials and businessmen.

Kirill, the former head of the church's foreign relations department, succeeded Patriarch Alexy II, who died in early December after almost two decades at the helm of the church.

Alexy, the church's first post-Soviet leader, led his institution during an era when millions of Russians returned to their historic faith. The church now claims to minister to a flock of 100 million believers in Russia, the former Soviet republics and across the globe.

But polls show that only about five per cent of Russians are observant believers, and only 30 per cent of the population believe they should follow the moral teachings of the church.

Kirill, who has long been Alexy's deputy, has been critical of tolerance of homosexuality, abortion, multiparty democracy and the division of secular and religious authority.

Kirill adheres to nationalist ideas about Russia's role in the world and supports the idea that Russian civilization is fundamentally different and opposed to Western concepts.

He has repeatedly advocated expanding the church's outreach to younger and wider audiences, and has long pushed for introduction of Orthodox religious classes in schools.

Kirill is an unusually public and outspoken religious figure in the church known for its traditionalism and resistance to change. He appears on television shows and frequently voices his opinion on secular matters, including Russia's current economic crisis.

Kirill will face opposition from a strong conservative movement within the church that sees him as too modern and too eager for a rapprochement with the Roman Catholic Church. Among the changes Kirill is likely to initiate is wider use of Russian language in services instead of the archaic Church Slavonic and permission for women to wear trousers inside churches.

"He will have an uneasy choice -- to initiate reforms and turn the church into a lively body that responds to the needs of modern man, or reject even superficial novelties and stick to the undying past," said religious expert Boris Falikov.

On the day after his election, Kirill pledged to refrain from initiating "topdown reforms that hurt people," but cautiously promised changes, the Interfax news agency reported.

"God forbid any patriarch from going down in history as a reformist," Interfax quoted Kirill as saying. "But there are changes growing from within people's lives."

As a skilled politician and veteran diplomat, Kirill is expected by some to seek a more muscular role for the church, which has served the state for much of its 1,000-year history.

Church and state are officially separate under the post-Soviet constitution, but ties have tightened again since Vladimir Putin came to power in 2000.

Before he became patriarch, Kirill was in charge of contacts with the Vatican and met with Pope Benedict XVI in December 2007.

But after his election, church leaders ruled out a meeting between pope and patriarch -- the unrealized dream of the late Pope John Paul II.

The Russian church accuses the Vatican of trying to convert Russians to the Catholic faith. There have also been disputes over property and influence in Ukraine, where both churches have large flocks.

Alexy's death was followed by an intense election campaign within the church. In becoming his church's supreme cleric, Kirill defeated a powerful Moscow bishop and the leader of the church in the neighboring country of Belarus.

The new church leader was born as Kirill Gundyaev into a priest's family in 1946 in Leningrad, now St. Petersburg. He advanced in the church hierarchy at a time when it was closely monitored by the KGB and Politburo, and clerics who objected to government control were routinely harassed and imprisoned.

Kirill served under two patriarchs who were elected from Politburo-provided one-man lists, and became an archbishop in the late 1970s.

He was appointed the head of the church's foreign relations department after the 1988 millennial celebration of Russia's conversion to Christianity, an event seen as a turning point in relations between the Kremlin and the church. Kirill became an influential figure under Alexy, who was elected in 1990.

In 1992, Kirill strongly opposed pressure to create a church commission to clarify links between KGB and the church. The commission, however, was formed and concluded that most of church leaders, including Kirill, had provided information to the security service.

Kirill denied the claim.