The Orthodox church's growing influence in Russia threatens to erode the separation of church and state and upset other officially-recognised religions, leading academics warned President Vladimir Putin earlier in the week.
"We are becoming increasingly concerned by the growing role of clerics in Russian society, by the Church's penetration into all facets of social life," several scientists, including two Nobel prize winners, said in an open letter to Putin.
The Christian Orthodox church has enjoyed a dramatic revival in its fortunes since the collapse of the Soviet Union in 1991.
But the letter, text of which was published in several national newspapers, implied criticism of the Kremlin chief for his overt sponsorship of church activities.
Once an ex-spy with the KGB secret police which treated priests as subversives, Putin says he is a an Orthodox believer and he turns out for major Orthodox festivals, often accompanied by a long retinue of senior state officials.
The signatories to the letter said giving preference to the Orthodox chuch could upset the delicate ethnic and religious balance in the vast country that is also home to up to 20 million Muslims, as well as followers of dozens of other faiths.
The signatories included Zhores Alferov and Vitaly Ginzburg, who have won Nobel Prizes for science, and eight other distinguished scientists who are senior members of the Russian Academy of Sciences.
"The constitution of the Russian Federation declares that our state is secular," the letter said.
The fresh concern about the Orthodox church's mounting influence was triggered by a proposal to teach Orthodox studies as part of the standard school curriculum and to reconise theology as a science.
"One could wonder, why on earth theology -- a set of religious dogmas -- should be regarded as a science?" said the letter.
"How can one be so scornful towards other confessions? Doesn't it smack of Orthodox chauvinism?," the scientists wrote.
Ethnic Russians -- most of them either Orthodox believers or people who class themselves as belonging to Orthodox culture -- make up over 80 percent of the nation's population.
Russia's Muslims are estimated to number between 14 million and 20 million, Jews up to 2 million, Buddhists around a million and Catholics some 600,000.
"In the long run, the Church hierarchy should think better about where this policy is leading -- to the nation's consolidation or its disintegration," said the letter.
Father Ioann Sviridov, editor-in-chief of a Christian radio station with close links to the Orthodox hierarchy, said it would be a mistake to "overdramatise" the church's growing influence.
"There are respected priests with immense authority who exert huge moral -- rather than political --influence on society, and I don't see anything bad in this," he said.
