Pope Francis will on Sunday return to the island of Lesbos, the migration flashpoint he first visited in 2016, to plead for better treatment of refugees as attitudes towards immigrants harden across Europe.

On the second day of a landmark trip to Greece Francis will tour the temporary camp of Mavrovouni, where nearly 2,200 asylum seekers currently live.

Francis has long championed refugees, whom he called the "protagonists of a terrible modern Odyssey" in a speech to Greek officials and EU vice-president Margaritis Schinas on Saturday.

He was speaking in Athens which had gone without a papal visit for 20 years.

Ahead of the Lesbos visit, 31-year-old Cameroonian camp resident Christian Tango said he hoped the pope would "carry the voice (of refugees) to the whole world".

As with other residents, Tango is only allowed to leave the camp once a week but on Sunday, he will get to speak to the pope.

The Mavrovouni tent camp was hurriedly erected after the sprawling camp of Moria, Europe's largest such site at the time, burned down last year.

Greek authorities blamed a group of young Afghans for the incident and security has been substantially enhanced ahead of the pontiff's visit with 850 police officers deployed.

In Cyprus, where the pope visited before Greece this week, authorities said Friday 50 migrants, including two Cameroonians stuck for months in the divided island's buffer zone, will be relocated to Italy thanks to Francis.

Officials have not ruled out the possibility that some migrants from Mavrovouni could accompany him back to Italy.

He had taken 12 Syrian refugees with him during his last visit in 2016.

- EU 'torn by egoism' -
At the start of his visit on Saturday, Francis said Europe was "torn by nationalist egoism" instead of acting as an "engine of solidarity" on migration.

"Today, and not only in Europe, we are witnessing a retreat from democracy," he said, warning against populism's "easy answers".

In 2016, Francis had visited Moria with Bartholomew I, the spiritual leader of the world's Orthodox Christians, and Archbishop Ieronymos II, head of the Church of Greece.

In a ceremony later held at the port of Mytilene, the three leaders held mass to bless the thousands who had died trying to reach Europe.

The Mavrovouni camp currently holds 2,193 people and has a capacity of 8,000, the facility's deputy chief Dimitris Vafeas told ERT state TV this week.

"Everyone is staying in containers in good conditions. Asylum procedures are significantly improved, no one spends more than three to four months in the camp -- except exceptional cases," he said.

With EU funds, Greece is building a series of "closed" facilities on Greek islands with barbed wire fencing, surveillance cameras, X-ray scanners and magnetic gates that are closed at night.

Three such camps have opened on the islands of Samos, Leros and Kos, with Lesbos and Chios to follow next year.

NGOs and aid groups have raised concerns about the new camps, arguing that people's movements should not be restricted.

Thirty-six groups active in Greece this week wrote to Francis raising the plight of people in the camps and requesting his help to halt illegal pushbacks of migrants allegedly by Greek border officers.

Greece vehemently denies the claims, insisting its coastguard saves lives at sea.

The pope's Sunday visit to Lesbos will be shorter than his last, officials said, as he will fly back to Athens to hold a mass for some 2,500 people at the Megaron Athens Concert Hall.

On Lesbos, the pontiff will deliver an Angelus prayer in a camp tent in the presence of Greek President Katerina Sakellaropoulou, EU vice-president Margaritis Schinas and Greek Migration Minister Notis Mitarachi.

"He is clearly interested in seeing refugees," Vafeas said, adding that the pontiff would meet with two "randomly chosen" families.

The pope will return to Rome on Monday.