Pope Francis on Saturday condemned "belligerent nationalisms" and called for a pan-European response to migration to stop the Mediterranean, where thousands have drowned, from becoming "the graveyard of dignity".
Immigration issues dominated his 27-hour trip to Marseilles, a French port that for centuries has been a crossroads of cultures and religions.
On Friday, he said migrants who risk drowning at sea "must be rescued" because doing so was "a duty of humanity" and that those who impede rescues commit "a gesture of hate".
Francis doubled down in a long speech on Saturday morning when he concluded a Church conference on Mediterranean issues.
"There is a cry of pain that resonates most of all, and it is turning the Mediterranean, the 'mare nostrum', from the cradle of civilization into the 'mare mortuum', the graveyard of
dignity: it is the stifled cry of migrant brothers and sisters," he said, using Latin terms meaning "our sea" and "sea of death".
On the flight to Marseilles on Friday, Francis was moved as he was shown a picture of a migrant child by Reuters photographer Yara Nardi. The photo was a close-up shot of the eyes of 18-month old Prince, who with his mother Claudine Nsoe, had arrived by sea on the tiny Italian island of Lampedusa from North Africa.
President Emmanuel Macron, other government officials and European Central Bank President Christine Lagarde attended a papal Mass on Saturday afternoon for 50,000 people who packed the city's Velodrome stadium. Authorities said another 100,000 lined his route to the stadium.
Left-wing politicians have criticised Macron over his decision to attend the Mass, saying it violates strict separation of state and faith, known as laïcité. He said he was attending out of respect for the pope.
At the conference on Saturday morning, Francis called on people to "hear the cries of pain" rising from migrants seeking a better life.
"How greatly we need this at the present juncture, when antiquated and belligerent nationalisms want to make the dream of the community of nations fade!" he said. He did not name any countries.
Governments in several European countries, including Italy, Hungary, and Poland, are led by outspoken opponents of immigration. The pope also contested those who characterise migration as an "invasion," saying it is a long-term issue that would have to be met with compassion.
He called for an expansion of legal paths to immigration with emphasis on accepting those fleeing war, hunger and poverty, rather than on "preservation of one's own wellbeing".
According to UN Refugee Agency UNHCR, about 178,500 migrants have come to Europe via the Mediterranean this year, while about 2,500 died or went missing.
While Francis has said often that migrants should be shared among the 27 EU countries, his overall openness towards migrants, including once calling their exclusion "scandalous, disgusting and sinful," has riled conservative politicians.
The pope, who was returning to Rome after the Mass, began the day by visiting a centre for the needy in Marseilles' Saint Mauront district, one of France's poorest, run by the order of nuns founded by Saint Mother Teresa.