Hundreds of Orthodox believers joined hands in cities across Russia Sunday in a "day of protest and prayer" against the "aggressive and expansionist" Roman Catholic Church.

Experts say the Kremlin, at least, may be listening. Within the past month, Russian security services have inexplicably deported two Catholic priests, one a bishop who had been rebuilding their church in Russia after the long communist winter.

"Our goal is to protect Russian statehood and our church against Catholic expansionism," says Ivan Frolov, press secretary of the Union of Orthodox Citizens, a lay organization closely linked to the Orthodox Church, and one of the organizers of Sunday's demonstrations.

The protests were backed by the small, centrist Peoples' Party, whose leader in the Duma, Gennady Raikov, lashed out publicly last week at the Vatican, saying: "The Russian state must show that it is not only able to defend the physical borders of the country, but also its spiritual values."

Last week Bishop Jerzy Mazur, a Polish citizen who heads the world's largest Catholic diocese in the sprawling Siberian territory of Irkutsk, was stopped at Moscow airport by border guards and saw his multiple-entry visa cancelled without explanation. Earlier, an Italian priest who had worked in Russia for a decade, Father Stefano Caprio, was barred from the country. A Catholic monk, Damian Stepien, alleges that Moscow police defaced his passport and tossed it in a waste bin after he told them he was a Catholic during a street check of documents last week.

"This pattern of events suggests the Russian government may be helping the Orthodox Church in its desire to eliminate competition on Russian territory," says Kamaludin Gadjiev, an expert on religion with the Institute of World Economy and International Relations in Moscow.

The Russian government has offered no explanation of its role in the rising tensions. Foreign Ministry spokesman Alexander Yakovenko, commenting on the expulsion of Bishop Mazur, told journalists only that "competent organs" had acted in accordance with Russian law. "The basis for the relevant decision is serious complaints about the activities of the Vatican's senior representative," in Russia.

According to its post-Soviet Constitution, Russia is a secular state. But for over 1,000 years, the Orthodox Church has been closely identified with Russian statehood. In the 17th century, Peter the Great abolished the office of the church's independent patriarch, or spiritual head, and replaced him with the tsar. Soviet leaders revived the post of patriarch, but reduced the church to a wing of the state bureaucracy. …