Patriarch Kirill, the new leader of the world's 160 million Russian Orthodox, pledged at his enthronement on Sunday to keep his church united, recruit the young and open up dialogue with "sister churches."

Hundreds of dignitaries and thousands of ordinary worshipers packed Christ the Savior Cathedral to see Kirill enthroned as the 16th patriarch in an elaborate, three-hour ceremony.

Two metropolitans seated Kirill three times in the patriarch's green and white throne, chanting "axios," worthy, along with the clergy and the congregation.

The 62-year-old new patriarch will oversee the world's second-biggest Christian church, which has grown stronger, wealthier and more influential since the collapse of communism. Most Russians consider themselves Orthodox, and the church may play a key role in molding the population's response to the economic crisis gripping the country.

Kirill's predecessor, Alexy II, plunged into politics in 1991, condemning violence as a failed coup crumbled, and again in 1993, trying unsuccessfully to broker a peace deal between former President Boris Yeltsin and his hard-line opponents.

President Dmitry Medvedev and Prime Minister Vladimir Putin looked on at Sunday's ceremony, crossing themselves repeatedly. Grand Duchess Maria Vladimirovna, a descendant of the last tsar, also attended. Medvedev congratulated Kirill, saying his enthronement was a "huge event" that he hoped would lead to "a full dialogue in solidarity between the Russian Orthodox Church and the state."

Kirill, a relative liberal in Russia's highly conservative church, emphasized independence. He said relations with the government should be run on "a constitutional basis." The Constitution stipulates the separation of church and state.

The new patriarch said his priority was to bring God to young people. The church could not wait "in an age of moral relativism, when the propaganda of violence and depravity kidnaps the soul," for young people to come to it, he said.

Kirill also hinted that he may play a more active role as pastor of the 30 million Russian Orthodox believers living outside Russia.

Pledging to maintain church unity, Kirill said he would increase dialogue with other former Soviet republics and the churches in them, as well as with "sister churches," but he did not mention ties with Catholics specifically.

Kirill, formerly a metropolitan who ran the church's external relations department, has spoken in favor of warming ties with Rome. He is one of a few top Russian Orthodox clergy to have met Pope Benedict XVI.

Sunday's ceremony was rich in the traditions of the Eastern Orthodox Church, which considers itself the true survivor of original early Christianity. Prince Vladimir of Kiev adopted Byzantine Christianity as the state religion in 988. Priests intoned the sonorous bass tones of the ancient Orthodox liturgy, interspersed with bursts of praise and thanks for the patriarch from choirs on the cathedral's balconies.

Emissaries from different branches of the Orthodox Church, the Vatican and other religions crowded the cathedral, along with ambassadors, government figures and ordinary worshipers.