More than 660,000 Ukrainians had fled to neighbouring countries by 1 March with Poland welcoming more than half of them.
ADVERTISEMENTPope Francis thanked the Polish people for "opening your borders, your hearts" to Ukrainians fleeing the Russian invasion of their country.
"I warmly greet all the Polish people," the pope said during his audience on Catholic Ash on Wednesday.
"You are the first ones who have supported Ukraine opening your borders, your hearts, the doors of your homes to the Ukrainians who are escaping the war. You are generously offering everything that is necessary so that they can live in a dignified way despite the dramatic moment. I am profoundly grateful, and I bless you from my heart," he also said.
Russia attacked Ukraine on 24 February, moving its troops through their shared border as well as through Crimea. Kyiv has also said Russian military equipment and forces crossed into the country from Belarus.
More than 660,000 Ukrainians — mostly women and children as men aged 18 to 60 are being conscripted —had fled to neighbouring countries by 1 March, according to figures from the UN refugee agency.
Poland had welcomed 377,000 of them.
The leader of the Catholic Church also heaped praise on a Franciscan Friar of Ukrainian origin, Marek Viktor Gongalo.
"This Franciscan Friar is speaking now in Polish but he is Ukrainian and his parents are in this moment in an underground refuge to protect themselves from bombs in a place near Kyiv. And he continues to carry out his duties here, let's accompany him and all the people who are suffering under the bombardment, his elderly parents and the many elderly who are now hiding underground to stay safe.
"We carry thoughts of these people in our hearts. (Turning to friar) and thanks to you for continuing your work," he said.
Pope Francis also called for a day of fasting and prayer for Ukraine.