MORIA, Greece -- Municipal crews washed down streets with pressure hoses, pruned trees and tidied up building facades on the Greek island of Lesbos on Friday, a day before a visit by Pope Francis that rights groups hope will highlight the plight of refugees who fled war-torn homelands only to be denied entry to Europe.

The Vatican insists Francis' five-hour visit is purely humanitarian and religious in nature and isn't a direct criticism of the European Union's new deportation plan. But the image of Francis meeting with refugees slated for deportation will bring the controversy back to the world's attention.

Francis will be joined by Ecumenical Patriarch Bartholomew, the spiritual leader of the world's 300 million Orthodox Christians.

The head of the Orthodox Church of Greece, Athens Archbishop Ieronymos II, arrived in Lesbos on Friday ahead of Francis' visit. He said the ecumenical mission had one aim: "To take the problem we have been dealing with for so long and make it an international issue -- to be not just a problem for Greeks, but for Europe and for all humanity."

The three religious leaders will visit a camp on Lesbos where 2,300 people are being detained for deportation to Turkey under an agreement between Ankara and the EU to ease the flow of migrants into Europe.

"The pope's visit comes at a pivotal moment: Right as Europe is gearing up to send thousands of refugees back to Turkey, locking them up in the meantime in horrible conditions," Gauri van Gulik, deputy Europe director at Amnesty International, told The Associated Press. "These are people who fled the horrors of Islamic State, the Taliban, bombings in Syria and more. They deserve Europe's protection and care, and hopefully the pope can shed light on their plight."

Hundreds of police took up positions Friday on Lesbos, including anti-terrorism officers, riot squads and plainclothes officers. They descended on the Moria detention camp where the religious leaders plan to meet 250 asylum-seekers Saturday in a large tent, make a public address, and join some detainees for lunch.

As a police helicopter buzzed overhead, police set up a perimeter around the freshly painted camp to block access to the media.

Lesbos' mayor and island officials urged residents to welcome Francis when he visits the island's main town of Mytilene -- describing the trip as a blow to "racism, fanaticism and xenophobia."

But not all islanders were in the mood for celebration.

"I don't trust leaders. I trust people. You can't side with the refugees and with the politicians deporting them. So I think the pope's visit will just muddy the waters," said hospital doctor Stathis Pavlou, who joined a small protest Friday outside the detention camp. "We should be helping these people, not locking them up."

Refugees and migrants reaching Greece from across the sea have been arrested since March 20, when the EU-Turkey deal took full effect. Assisted by police officers sent from across the EU, Greece has so far deported 325 migrants, most on small ferries from Lesbos, which lies just 8 kilometres (6 miles) from Turkey.

But most will have to wait months to have their asylum applications reviewed as they remain at camps first created to register masses of migrants heading toward central Europe, but which are now being used to stop them.

"It's clear conditions at the camps are unacceptable. There are unaccompanied minors locked up behind barbed wire," said Jerome Oberreit, secretary general of the relief agency Doctors Without Borders. "I hope a leader who influences opinion, like the pope, will voice the worry that Europe is actually not going the right way, and that this deal will have repercussions."

More than a million newcomers travelled to the EU last year, about half landing on the beaches of Lesbos, a few of which are still littered with orange life vests. The migration was halted earlier this year after Austria and the Balkan countries imposed strict border controls -- leaving some 50,000 people stranded in Greece.

Pakistani migrant Ayaz Islam Khan spoke to the AP through a razor-wire fence Friday at the Lesbos camp when police briefly wandered away.

"It's not good here. Not good. We came across Iran and Turkey. The sea was very bad when we (travelled) to Greece. And now they will send us back," he said. "I hope the pope can help us. All of us."

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Nicole Winfield in Rome contributed.