The latest developments in Pope Francis' visit to Cuba:

1:15 p.m.

A Vatican spokesman says Pope Francis and Fidel Castro exchanged gifts of books during their half-hour meeting at the former Cuban leader's home.

Federico Lombardi says the pontiff presented Castro with a volume written by a Jesuit who taught him at the Catholic school he attended as a child.

Castro gave the pope a collection of his own conversations about religion with Brazilian cleric Frei Betto.

11:10 a.m.

Cuban state-run website Cubadebate has changed the logo on its homepage and Twitter account in honor of Pope Francis' visit.

The usual logo consisting of red and black semicircles and white arrows has been replaced by a graphic representation of the tall papal headgear known as the mitre, emblazoned with a cross.

It's accompanied by the words "Welcome to Cuba," in Spanish in place of Cubadebate's usual tagline: "Against Media Terrorism."

10:40 a.m.

Cuban President Raul Castro is the first to greet Pope Francis after the pontiff celebrated Mass in Havana's Revolution Plaza.

Francis also chatted briefly with Argentine President Cristina Fernandez and island religious leaders.

Two aides steadied the pope as he climbed the stairs to the altar, and again when he descended. He suffers from sciatica and occasionally walks with a limp.

10:21 a.m.

Pope Francis is begging Colombia's government and largest guerrilla army to end South America's longest-running conflict, saying they cannot allow another failure to derail peace efforts.

Francis issued the appeal Sunday from Revolution Plaza in Havana, where peace talks underway for more than two years between the Revolutionary Armed Forces of Colombia and representatives of Bogota aim to end a half-century of fighting.

He said: "May the blood shed by thousands of innocent people during long decades of armed conflict" sustain efforts to find a definitive peace.

Francis added: "Please, we do not have the right to allow ourselves yet another failure on this path of peace and reconciliation."

The church's first Latin American pope recently helped nudge forward the historic reconciliation between the United States and Cuba with a personal appeal to the leaders of both countries.

9:45 a.m.

Pope Francis is urging Cubans to look out for one another and not just judge others based on what they are or are not doing.

Francis directed the message to thousands of Cubans gathered Sunday for his first Mass in Havana's Revolution Plaza. He told them that those who want to be great must serve others, and not be served by them. He said Cubans should avoid "judgmental looks."

He said "All of us are asked, indeed urged, by Jesus to care for one another out of love ... Without looking to one side or the other to see what our neighbor is doing or not doing."

It wasn't immediately clear what Francis was referring to. But many Cubans complain about the rigidity of a system in which virtually every aspect of life is controlled by the government, from cultural institutions to block-level neighborhood watch committees, in which people are excluded or lose benefits if they are perceived as being disloyal or unfaithful to the principles of the revolution.

That has eased in recent years, but it remains a problem in the eyes of many islanders and outside observers.

Many Cubans are also increasingly concerned about growing inequality, as those with access to foreign capital live better than others who struggle to feed themselves, generating jealousy and division within families and society at large.

9:15 a.m.

Cuban security personnel have detained at least three people who appeared to be trying to distribute leaflets ahead of Pope Francis's Mass in Havana's Revolution Square.

The officials dragged them away and picked up the flyers that were left on one of the streets surrounding the plaza. It's not clear what the protest was about. The three were in white T-shirts and were yelling before they were tackled and dragged away.

8:30 a.m.

Pope Francis is circling the crowd gathered for his first Mass in Havana, stopping his open-sided popemobile frequently to greet worshippers and kiss youngsters handed up to him.

Vatican and Cuban flags wave amid the throngs in Cuba's Revolution Square.

Cuban President Raul Castro is among those gathered for the Mass.

8:15 a.m.

The sun has risen over Havana's Revolution Plaza and already thousands of people have filled the square ahead of Pope Francis' first Mass in Cuba.

Believers and non-believers alike have streamed into the square, waiting for Francis to arrive by popemobile. The square's iconic metal portrait of Che Guevara competes with a huge poster of Christ facing the altar where Francis will celebrate Mass.

EARLIER STORY:

Pope Francis opens his first full day in Cuba on Sunday with what normally would be the culminating highlight of a papal visit: Mass before hundreds of thousands of people in Havana's evocative Revolution Plaza.

The morning Mass kicks off a busy day for Francis, including a formal meeting with President Raul Castro and a likely encounter with his 89-year-old brother, Fidel. Francis will finish the day with an evening vespers service in the San Cristobal cathedral and meet with Cuban young people.

Young and old turned out in droves Saturday to line Francis' motorcade route and welcome a man that many credit with helping bring about the thaw in relations between Cuba and the United States.

"This visit is like a breath of hope blowing over Cuba," Diego Carrera, a retiree, said as he awaited Francis at the start of a 10-day trip to the onetime Cold War adversaries.

Francis wrote a personal appeal to Presidents Barack Obama and Raul Castro and hosted their delegations at a secret meeting at the Vatican last year to seal a deal after 18 months of closed-door negotiations. Since then, the two leaders have reopened embassies in each other's countries, held a personal meeting and at least two phone calls and launched a process aimed at normalizing ties in fields ranging from trade to tourism to telecommunications.

Upon his arrival, Francis plunged head-first into the rapprochement, urging the Cuban and U.S. governments to push forward on their newly forged path and "develop all its possibilities."

The Vatican has long opposed the U.S. trade embargo on the grounds that it hurts ordinary Cubans most, and is clearly hopeful that detente will eventually lead to a lifting of sanctions.

But only the U.S. Congress can remove the embargo. Francis will visit Congress next week at the start of the U.S. leg of his trip, but it's not known if he will raise the issue there.

Standing with Raul Castro by his side, Francis said the developments over recent months have given him hope.

"I urge political leaders to persevere on this path and to develop all its possibilities as a proof of the high service which they are called to carry out on behalf of the peace and well-being of their peoples, of all America, and as an example of reconciliation for the entire world," he said.

Castro, for his part, criticized the embargo as "cruel, immoral and illegal" and called for it to end. But he also thanked Francis again for his role in fostering "the first step" in a process of normalizing relations.

The pope's message on Sunday is likely to be less political and more pastoral.

Francis has said he is coming to Cuba as a messenger of mercy, aiming to give solidarity to a long-suffering people and church.

The island's communist government never outlawed religion per se. But it came close, closing religious schools after Fidel Castro came to power in 1959, expelling priests and sending others to prison or work camps, including the current archbishop of Havana, Cardinal Jaime Ortega.

Castro began easing prohibitions on faith in the 1990s, removing constitutionally enshrined atheism ahead of a visit by Pope John Paul II and reinstating Christmas as a public holiday soon after.

The Catholic Church today has quietly established itself as practically the only independent institution with any widespread influence on the island. Expanding into areas once utterly dominated by the state, the church is providing tens of thousands of people with food, education, business training and even libraries stocked with foreign best-sellers.

But it still is seeking more freedom to spread the faith: Church authorities have long wanted to run full-time private schools and get religious programming on state-run airwaves, both of which the government has resisted

In his airport arrival speech, Francis said he hoped his visit would renew the bonds of friendship so the church can continue to do its job "with the freedom and the means necessary."

While most Cubans are nominally Catholic, fewer than 10 percent practice their faith.

Magaly Delgado, an accountant, said she would be at the Mass on Sunday because "I'm a believer and this pope interests me a lot because of all the change that he's making."