German President Joachim Gauck praised the work of Protestant Reformation leader Martin Luther on Monday, saying the Renaissance monk had "to a large extent" brought Christianity into modernity. Gauck, himself a pastor, was on hand in Berlin as Germany's protestants began a year-long celebration marking 500 years since the Reformation began with Luther nailing his famous 95 theses to the wall of All Saints' Church in Wittenberg, to the south of Berlin.

In a memorial church service that was also attended by a number of prominent Catholics in Germany, such as Cardinal Karl Lehmann, Gauck highlighted the value of mercy and the Grace of God. He said it was the "most important word of the Reformation."

Pope Francis himself attended a Reformation memorial service while on a visit to Sweden, the first time in history the leader of the Roman Catholic church has made such a high-profile showing of commemorating the event.

Francis had high praise for Martin Luther, and said the rise of Protestantism had "helped give greater centrality to sacred scripture in the Church's life." After leaving the service in Lund with King Gustav and Queen Silvia, the pontiff said that both Protestants and Catholics sought to uphold "the true faith."

Martin Luther changed Europe forever when he published his critique on the excesses of the Church on October 31, 1517. A monk and professor of theology at the University of Wittenberg, Luther excoriated practices such as selling "indulgences" - the issuing of a paper purporting to absolve somebody of their sins in exchange for a religious financial donation. 

The fallout ultimately ushered in centuries of religious conflict between Protestants and Catholics, partially breaking the grip the Vatican had possessed on the continent.

es/msh (AFP, AP, dpa)