Pope Francis has hailed Poland's native son St John Paul II, who was the first Polish pope, as a meek and powerful herald of mercy on his five-day visit to the country.

Francis also hailed the countless "ordinary yet remarkable people" who held firm to their Catholic faith throughout adversity in the former Communist-ruled nation.

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The Argentine pontiff, who had never been to Eastern Europe before this week's pilgrimage, gazed in awe for several minutes at the Jasna Gora monastery shrine's iconic image of the so-called Black Madonna and Child.

The faces in the images are blackened by centuries of varnish and candle soot since the artwork became the object of veneration starting in the 14th century.

Then, during an outdoor Mass before tens of thousands, Francis lavished praise on a legacy of steadfast Polish Catholic faith as he urged Poles to hold fast to their faith.

As Pope Francis walked up to the altar he tripped and fell over, but was quickly helped to his feet by others.

The Herald:

The Mass was held in celebration of the 1,050th anniversary this year of Poland's acceptance of Roman Catholicism.

The baptism of a medieval king in 966 put the nation on course to be part of the Latin-speaking world, setting it apart from Orthodox nations on its borders.

Pope Francis is urging today's Poles to stay united, as their nation is divided over such issues as how to view refugees and migrants, especially those who are not Christians.

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During an outdoor Mass before tens of thousands of people, Francis prayed that Poles would have "the desire to leave behind all past wrongs and wounds, and to build fellowship for all, without ever yielding to the temptation to withdraw or to domineer."

The Herald:

Worry about bad weather prompted a last-minute change in his day's travel plans, with the pontiff opting to take a car instead of a military helicopter to Czestochowa. But the grey skies held into the Mass.

Francis will have his first big meeting with the young faithful in a Krakow meadow on Thursday evening.

Pope Francis made an unscheduled stop at a clinic to visit and pray for comatose Cardinal Franciszek Macharski, an-89-year-old retired prelate who had been archbishop of Krakow.

Cardinal Marcharski had replaced Cardinal Karol Wojtyla in the post after the latter was elected pontiff and became John Paul II in 1978.

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With John Paul a national hero as well as a beloved saint, Francis finds himself in a deeply Catholic country that is attached to Czestochowa, where the shrine is located, and where a main boulevard is named after John Paul.