LESBOS (Greece) • Migrants wept at his feet, kissed his hand and begged for Pope Francis' help yesterday at a Greek refugee camp on the front line of Europe's migrant crisis which has claimed hundreds of lives in the past year.

At a sprawling fenced complex on the Aegean island of Lesbos, adults and children broke down in tears, pleading for help after their onward journey to Europe was cut short by a European Union decision to seal off a migrant route used by a million people fleeing conflict since early last year.

Pope Francis, leader of the world's 1.2 billion Roman Catholics, shook hands with hundreds of people as hundreds more were penned behind metal barriers at the Moria camp, which holds some 3,000 people.

"Freedom, freedom," migrants chanted as the Pope walked through the hillside facility in the scorching sun. Some women wailed.

Three families of Syrian refugees boarded Pope Francis' plane heading back to the Vatican after his lightning visit, a Reuters witness said.

"The Pope has desired to make a gesture of welcome regarding refugees, accompanying on his plane to Rome three families of refugees from Syria, 12 people in all, including six children," a statement issued by the Vatican said.

Pope Francis said in a scripted speech at the refugee camp: "I want to tell you, you are not alone.

"...As people of faith, we wish to join our voices to speak out on your behalf. Do not lose hope!" he said, flanked by Patriarch Bartholomew, spiritual leader of the world's Orthodox Christians, and Greek Archbishop Ieronymos.

On at least three occasions, adults fell to the feet of the pontiff, weeping and begging for help.

One woman wearing a crucifix broke through a police cordon and flung herself at the Pope's feet.

"No camp, no camp," the woman sobbed. "I want to go."

In a tent where Pope Francis met with migrants, a little girl with pigtails dressed in pink and white bowed at his feet.

A man broke down.

Migrants slipped pieces of paper into his hand as he passed by, which he handed to an aide.

The Pope has often defended refugees and urged Catholic parishes in Europe to host them. His first trip after becoming pontiff in 2013 was to the Sicilian island of Lampedusa, which, like Lesbos, has received thousands of refugees.

Hundreds of people have died making the short but precarious crossing from Turkey to the Lesbos shores in inflatable dinghies in the past year. The island is full of unmarked graves.

AGENCE FRANCE-PRESSE, REUTERS