Pope Benedict XVI Thursday called on Poland to rise above divisions originating in the country's communist past.

Addressing clergy in St John's Cathedral in Warsaw, on the first day of his trip to the homeland of his Polish-born predecessor John Paul II, the pope entered the debate over how to deal with alleged former agents of the communist-era secret police, including Catholic priests.

The ruling conservatives, who came to power at the end of last year, want purges and legal action, while others, particularly left-wing politicians, argue that 17 years after the fall of communism it is time to show leniency and move on.

Benedict XVI called on the younger generation to refrain from all "arrogant judgement against previous generations who lived in different times and other circumstances."

He called for restraint in making "facile accusations in the absence of real proof" and for those who stand accused to show "humble sincerity and not to deny the sins of the past."

A week before the pope's arrival in Poland, Polish priest Michal Czajkowski, who is known in his native land for his work in reconciling Christians and Jews, was accused in a press report of having been a communist agent for 24 years.

"The country of my beloved predecessor"

"I have come to follow in the footsteps of John Paul II, along the path of his life," Benedict said in Polish to cheers from the crowd of airport staff and dignitaries who were on hand to greet him. "This is not just a sentimental journey, but a journey of faith."

"I want to drink at the abundant spring of your faith, which has flowed incessantly for more than a millennium," he added.

Benedict's Alitalia flight from Rome touched down at Warsaw's Okecie airport shortly before 11:00 a.m.

A blustery wind ruffled his white papal cloak as he descended the steps of the plane to hymns entoned by a choir of airport employees.

Gusts of wind bore the sound of tolling church bells while Benedict shook hands warmly with state and church dignitaries, including Polish President Lech Kaczynski, Cardinal Primate Jozef Glemp and Archbishop of Krakow Stanislaw Dziwisz. A military band stood to attention.

"I am happy to be here, among you, on the soil of the Polish republic," he said. "I so wanted to visit the country of my beloved predecessor, the servant of God John Paul II, and to be here, among his country people."

Kaczynski, in a nod to often turbulent Polish-German relations in the past, welcomed the pope and spoke of spiritual reconciliation.

"Providence has deemed that a German has succeeded a Pole on the throne of Saint Peter," he said. "Our two peoples, who are very close, have often been separated by history. Today we feel that true reconciliation can only be achieved on a spiritual dimension."

"Long live the pope"

After the official welcome, Benedict set off in a motorcade, bound for St. John's Cathedral in the centre of Warsaw, to meet with members of the clergy.

Thousands of Poles lined the streets of the capital to welcome the pope. Some cried, in Polish, "Long live the Pope," others held aloft the yellow and white flag of the Vatican, letting it flutter in the brisk spring breeze.

After passing through the Old Town, carefully rebuilt after it was completely destroyed in World War II, the papal motorcade drove past the monument to the victims of the Warsaw ghetto, where Poland's Nazi occupiers isolated the capital's thriving pre-war Jewish community.

But to the disappointment of the crowd gathered there, it neither slowed nor stopped to allow the pontiff to descend and pay tribute to the Jews who were terrorized in wartime Warsaw.

The pope also passed in front of a monument to Poles deported and killed in the former Soviet Union, and one to the tragic 1944 Warsaw uprising against the Germans.

The city was almost entirely destroyed in the closing phases of World War II, and the country's Jewish population of around 3.5 million obliterated.

Like most German boys, Benedict was enrolled into the Hitler Youth, but he took no part in fighting and later deserted the army.

Going to Auschwitz as a Catholic

The first day of the papal visit was to be devoted mainly to meetings with Polish officials and members of the clergy.

On Friday, Benedict XVI will lead a huge open-air mass in Warsaw's central Pilsudski Square, which is expected to draw around one million faithful.

In his speech at the airport, Benedict spoke in Italian about the rest of his itinerary after Warsaw, which will take him south to key sites in the life and papacy of John Paul II, culminating Sunday at the Nazi death camp at Auschwitz-Birkenau.

"I hope to meet there survivors, the victims of Nazi terror, from the many nations which suffered this tragic oppression," Benedict said. "We will pray together that the wounds of the past century are healed by the medicine of God, who calls on us to forgive each other and offers us the mystery of the Divine Mercy."

On the flight to Poland, Benedict had told reporters that he was going to Auschwitz "first and foremost as a Catholic," not as a German.

"It is very important to understand that we are Catholics and Catholicism embraces all nationalities," he said.