Pope Benedict XVI celebrates mass in Warsaw, Friday

Pope Benedict XVI has celebrated his first outdoor mass in the Polish capital's Pilsudski Square, where his predecessor, Pope John Paul II, inspired Poland's Solidarity movement against communist rule in a historic 1979 visit.

An estimated crowd of about 300,000 people gathered in the Warsaw square amid heavy rain Friday. In his sermon, Pope Benedict challenged the view that there are no absolute values and defended the church's unchanging traditional beliefs.

He warned the faithful against those who, he said, "seek to falsify the Word of Christ and remove from the Gospel those truths that in their view are too uncomfortable for modern man."

The pontiff arrived in Warsaw Thursday. He is scheduled to travel to several cities in Poland during his four-day trip.

On Sunday Pope Benedict is to visit to the notorious Auschwitz death camp, where the Nazis killed more than one million Jews in the 1940's.

Upon his arrival, the German-born pontiff said his trip is intended to stress the importance of reconciliation and expressed hope it would heal some of the wounds of the past.

He also warned against what he called the "arrogant claim" of judging earlier generations who lived in different circumstances.