The stain on relations between Russia and Poland can be overcome through faith and forgiveness, a Russian Orthodox religious leader said last weekend.

Patriarch Kirill, head of the Russian Orthodox Church, said in a sermon Sunday at the Holy Mount Grabarka in Poland that lingering feelings of mistrust between Polish Catholics and Russian Orthodox Christians can fade through forgiveness of historical wrongs.

The patriarch, wrapping up a four-day visit to Poland, cited a joint memorandum he and Polish Archbishop Jozef Michalik signed Friday in Warsaw aimed at reconciling relations between two countries.

The document, he said, shows that "we are praying for the reconciliation between the Polish and Russian nations," Polish Radio reported.

Addressing the estimated 14,000 people gathered at the Polish holy site on the Feast of the Transfiguration, Patriarch Kirill said a Polish-Russian reconciliation can only take hold if it is faith-based, asserting that secular politicians, businesspeople and cultural activists can only do so much to bring it about.

"You in Poland, as well as us in Russia, in the former Soviet Union, know what it means to build a society without God," he said. "It is our experience which should show the whole world that it is not possible to build a just society ... if God is driven out."

Poland holds Russia responsible for many wrongs inflicted upon it, including the imposition of communist rule after World War II, during which the Catholic Church was persecuted by Marxist ideologues.

Another issue that continues to rankle Poland is the 1940 massacre of 22,000 Polish military officers and intellectuals in the Katyn Forest, ordered by Soviet dictator Josef Stalin.

Russia launched an investigation into the massacre in 1990, but the probe was halted 14 years later and its findings were classified. The Russian Parliament recognized in 2010 that Stalin ordered the executions, which were carried out by agents of the NKVD secret police.

Also speaking Sunday at Mount Grabarka was Metropolitan Sawa, head of the Polish Orthodox Church, the Voice of Russia reported.

"His Holiness Patriarch Kirill, whom we have been looking forward to seeing for a long time, has arrived," he said. "He came to see our faith, give us his blessing, and say his prayers for us, for our families, for our children, for our fatherland and for the world. His visit is a great joy to us."

Earlier in the week, the patriarch met with Polish President Bronislaw Komorowski, who said his country is committed to establishing good relations with Russia and cited the joint declaration as "an important landmark in the development of our relations."

"We are hoping it will turn over a new leaf in our bilateral relations," Komorowski told RT Television.

"Reconciliation can only be achieved through communication based on fundamental values such as freedom and responsibility, love for your neighbor and forgiveness ... We will strive to establish good relations between our countries."

Komorowski told the Russian broadcaster the "persecution and suffering experienced by our churches help us better understand each other."