By Castillo and Ariosto CNN - Pope Benedict XVI celebrated Mass in Havana's Revolution Plaza on Wednesday, steering clear of political statements but saying that "Cuba and the world need change."
The pope said that such change can come only if "each one is prepared to ask for the truth and if they decide to take the path of love, sowing reconciliation and brotherhood."
Earlier in his trip, the pontiff prayed for "those deprived of freedom" and said Cuba's Marxist political system "no longer corresponds to reality."
Many in Cuba and around the world listened closely to the pope's homily at the enormous open-air Mass to see whether he would expand on or be more forceful in his apparent criticisms.
But no such statements came, and the sea of faithful in the plaza listened intently to the ceremony.
Instead, the pope focused on the Bible story of three youths persecuted by the Babylonians who preferred to face death rather than denying their conscience and faith.
The pontiff spoke of freedom, but in the context of Christianity.
"The savior is the only one who can show the truth and give genuine freedom," he said.
He praised the emergence of religious freedom in Cuba but did not touch on political freedoms.
"It is with joy that in Cuba there have been steps so that the church can carry out its mission," but the country must continue to strengthen this path, he said.
After Wednesday's Mass, the pope met with former Cuban leader Fidel Castro, a Vatican spokesman said.
Castro, who stepped down from power in 2006 due to illness, had asked for a "modest and simple" meeting with the pope.
Conflicting reports emerged Wednesday over whether the pope had met with Venezuelan President Hugo Chavez. Two Cuban sources told CNN the pontiff met Tuesday with Chavez, who is in Cuba for cancer treatment. But Vatican spokesman Federico Lombardi said reports of the meeting were false.
Thousands of faithful packed Revolution Plaza to hear Wednesday's Mass.
The pope arrived in the so-called popemobile, his bulletproof vehicle, and slowly made his way to the altar via paths that cut across the crowd. At some points, the pope was just feet from the crowd, which shifted as people tried to get a closer look at the pontiff. Some sat on the shoulders of others for a better angle from which to take pictures or video.
Throngs of waving worshipers greeted the pontiff as the popemobile meandered around Revolution Plaza under the Caribbean sun. Rescue workers carried away at least three people who fainted in the heat.
"Every time the pontiff comes comes here, there's always some sort of transformative period for us afterwards," said Jorge Luis Rodriguez, a Havana resident who joined the thousands that filled the square on Wednesday.
But Cuban dissidents complained that police prohibited some activists from leaving their homes to attend the Mass and that others were detained.
Amnesty International said in a statement Wednesday that human rights activists were "facing a surge in harassment in a bid to silence them during the pope's visit."
Hundreds of government opponents were detained, threatened or stopped from traveling freely leading up to Pope Benedict XVI's arrival, according to the human rights group.
"The clampdown has seen an increase in arrests, activists' phones have been disconnected, and some have had their houses surrounded to prevent them (from) denouncing abuses during Pope Benedict's tour," the group said.
CNN could not independently confirm the reports.
Gerardo Ducos of Amnesty International told CNN en Español that the human rights organization had not been able to confirm details on the reported detentions with Cuban officials.
The pope's visit comes 14 years after Pope John Paul II addressed throngs of onlookers in the historic first papal visit to the island nation, in 1998.
Elsida Martinez, a Havana resident who said she watched from the square when John Paul spoke, said there was a noticeable difference between the two pontiffs. Cuba was also different, she said.
"When we saw John Paul, Cubans didn't really know anything about religion," Martinez said. "Now we're open more. We practice (religion) more. We believe more."
When John Paul came 14 years ago, "it was a different period in our history," said Camilo Ortiz, a 50-year-old Havana resident, but John Paul's visit still "had more power" than Benedict's.
"During that time, there were many difficulties here," Ortiz added. "Now, there are some changes, and things are a little better."
After the island's "special period," which began in the early 1990s after the dissolution of the Soviet Union, Cuba -- which had long enjoyed Soviet subsidies -- was confronted with a prolonged period of economic hardship.
When John Paul visited years later,
the country was still reeling from its effects.
Havana officials prepared for the pontiff's arrival by painting buildings and tacking posters across the city. They also put in place additional security measures around the capital.
Benedict, 84, arrived in Santiago de Cuba on Monday.
Tuesday evening, the pope met with Cuban President Raul Castro, both privately and publicly.
Raul Castro took over the reins when his older brother, Fidel, stepped down six years ago.
Cuba is Benedict's second stop on a tour that has also taken him to Mexico, where he denounced the violence-plagued drug war.
In Cuba, in response to the pope's remarks regarding the Marxist political system, a top Cuban official said that his country's system is sustainable and that it will not change.
"In Cuba, there will not be political reform," said Marino Murillo, vice president of the island's council of ministers.
But some Havana residents at Wednesday's Mass said they were optimistic.
"For me, there's a hope" that comes with Benedict's visit, Ortiz said. "There's a hope that something's going to change."