HAVANA (Reuters) - Pope Francis on Saturday descibed how he became emotional when he met a family of Syrian refugees who have been given shelter in the Vatican.

"There are wars, refugees who are escaping in this wave of migration away from wars," he told reporters aboard the plane taking him from Rome to Havana to start his nine-day trip to Cuba and the United States. "They are fleeing from death and seeking life," he said.

Pope Francis said that he became "emotional" at the Vatican, as he was leaving for the airport on Saturday morning, when he was greeted by a Syrian family that one of the parishes inside the tiny city-state is hosting.

"You could see the pain in their faces," he said.

Earlier this month, Pope Francis appealed to every parish and religious community in Europe to take in a family of refugees.

To set an example, the Pontiff asked the two parishes inside the Vatican, a sovereign city-state surrounded by Rome, to take in a family. "I think that today the world is thirsting for peace," he said.

An emergency meeting of European Union ministers this week failed to agree on a plan to share out some 160,000 newly arrived refugees, a measure aimed at relieving pressure on the region's border countries such as Italy, Greece and Hungary.

At the start of a nine-day tour of Cuba and the United States, the Pope exhorted Cuba and the United States on Saturday to set an example for the world by deepening the recent rapprochement that he helped secretly broker between the former Cold War foes.

His zucchetto skullcap flying off in the Caribbean breeze upon landing, the Argentine Pope used his arrival speech at Havana airport to praise this year's normalization of diplomatic relations. "I urge political leaders to persevere on this path and to develop all its potentialities ... as an example of reconciliation for the entire world," he said before riding his open-sided popemobile through roads thronged with well-wishers.

Better sensitised to the issue than predecessors because of his Latin American roots, the 78-year-old pontiff facilitated a back channel for secret talks and sent missives to Presidents Raul Castro and US President Barack Obama at a delicate stage in 2014.

That bore fruit with a prisoner swop, the opening of embassies, and an easing of some travel and trade restrictions, although a half-century-old economic embargo is still in place, only removable by the US Congress.

Pope Francis is a popular figure in Cuba and thousands lined the streets of Havana as he was driven to the papal nuncio's home, cheering, singing, and waving Cuban and Vatican flags.

"He brings hope for a better future for Cuba," said Ms Maria Antonia Iglesias, 65, waving a banner and clapping as Francisco passed by. "Love, peace and more unity is what we need between all Cubans: those who are here and those in the United States."

As on previous papal visits, the Cuban authorities rounded up some political opponents to prevent them from attending events around the visit, a dissident human rights group said.

Mr Raul Castro - who like his brother and former revolutionary leader Fidel Castro was baptised a Catholic and educated by Jesuits - received the Pope at the airport after his 12-hour flight from Italy. It was the third papal visit to Cuba in less than two decades.

Mr Castro thanked the Pontiff for his help with the US rapprochement, but also used his welcoming speech to criticise Washington's embargo and its occupation of the Guantanamo naval base on the eastern tip of the Caribbean island.

Cuba, he said, had been a model of internationalism and humanism in past decades. "We have done that while being blockaded, insulted, attacked, with a high cost in human lives and major economic damages."

Since reaching a historic breakthrough with Mr Castro in December, Mr Obama has come out against the embargo. On Friday, he issued new regulations weakening the embargo for a second time, using his executive authority to circumvent Congress.

Despite making Cuba constitutionally atheist and repressing Catholics in the early years after their 1959 revolution, the Castro brothers have relaxed that stance since the 1990s.

In his speech, Pope Francis sent greetings to Mr Fidel Castro, whom he is expected to meet. He also urged further backing for Cuban Catholics "so that the Church can continue to support and encourage the Cuban people in its hopes and concerns, with the freedom, the means and the space needed".

On a first-ever visit to Cuba, he is to celebrate Mass in Havana on Sunday in Revolution Square, where a huge picture of Jesus Christ has been hung alongside permanent images of revolutionary heroes Ernesto "Che" Guevara and Camilo Cienfuegos.

While in Cuba, he may well reiterate the Vatican's opposition to the US trade embargo. But once in the United States, the Pope may tread more lightly, aides said, to avoid the appearance of meddling in the web of legislation, interests, and decades-old resentments slowing the pace of change.

Cuba's ruling Communist Party will welcome any papal criticism of the embargo and may have to bear a corresponding call for greater political tolerance from the government, which still runs a one-party state and jails and harasses dissidents. "I hope for economic improvements, more freedom for religion, respect for human rights of all ideologies in our nation," said Mr Sandro Garcia, 39, strumming a guitar with others singing outside the nuncio's house as Francis arrived.

Mr Elizardo Sanchez, of the Cuban Commission of Human Rights and National Reconciliation, said between 10 and 20 dissidents had been detained to stop them attending papal events. "A similar number have been threatened or warned. It's preventive police repression," he said.

Among those held was the leader of the Ladies in White group in the province of Matanzas, Ms Leticia Ramos, who was going to lead a group of pilgrims to Havana, Sanchez said.

An estimated 60 per cent of Cuba's 11 million people are baptised Catholic, the Church says, but fewer than 5 per cent attend church, and a majority of Cubans are believed to follow Afro-Cuban religions.

"I'm a devout 'Santero' - the Church is for old people!" laughed Mr Eduardo Gutierrez, 19, sitting with his girlfriend on Havana's languid seafront. "But after what Francis has done for us, I am going to Revolution Square to show him my respect."