MEXICO CITY – Pope Benedict XVI donned a sombrero Sunday and stayed away from politics in his first open-air Mass in Latin America, urging Roman Catholics in Mexico to seek a pure heart and avoid “superficial and routine temptation.”

A crowd estimated by the quasi-official Notimex news agency at 400,000 people gathered under a blazing sun for the Mass in Guanajuato state.

On the third day of a six-day trip that also will take him to Cuba, the pontiff only tangentially touched on the violence roiling Mexico, saying he was aware of the “moments of both pain and hope” coursing through the region’s people.

Mustering strength limited by his age but walking without a cane, the 84-year-old Benedict sought to uplift Mexicans, saying the power of Christ is based on the ability to reach out to people’s hearts, not in the power of armies “to make others submit to force or violence.”

Before the homily, Archbishop Jose Martin Rabago of Leon told the pontiff that Mexicans have passed through years “of violence and death that have generated a feeling of fear.”

Enthusiasm for Benedict’s visit was low before his arrival. But excitement grew with wall-to-wall television coverage, building even to rapturous levels.

The outpouring of faith seemed to melt the pontiff’s staid demeanor, leading to several apparently unscripted and lighthearted moments.

One came early Sunday as Benedict’s white Popemobile approached the soaring outdoor altar. Someone handed a black sombrero of the type used by mariachis through a window to the pope. He good-naturedly put it on.

A day earlier, the pontiff briefly took an infant passed to him for a blessing through the window of his vehicle, and chuckled lightly when excited shrieks from youths interrupted his message from a colonial balcony in the city of Guanajuato.

Mexico remains the most Catholic country in the world after Brazil. In the 2010 census, 83 percent of Mexicans identified themselves as Catholic.

Shouts of “Long live the Pope!” and “Benedict, brother, you are now Mexican!” rang out as the Mass, the highlight of the visit to Mexico, ended and throngs streamed from Bicentennial Park between the cities of Leon and Guanajuato.

Afterward, Benedict boarded a Mexican army Super Puma helicopter for an aerial view of the Christ the King statue atop Cubilete hill, one of Mexico’s revered shrines.

It was on the flight over from Rome on Friday when the German-born pontiff made his strongest remarks regarding organized crime and drug trafficking that have left some 50,000 dead in Mexico since late 2006. He told journalists that Mexican society must “unmask the evil” and the “false promises and lies” of drug traffickers and that the Church bears a “great responsibility” for doing so.

U.S. clergy in Leon for the pontiff’s visit said the strong words were aimed at Mexican bishops wavering in a common approach toward the violence.

“They have been at odds on how to come up with a strategy,” said the Rev. Juan J. Molina, director of Latin American affairs for the U.S. Conference of Catholic Bishops. “This is going to send a message to the whole body of Mexican bishops to do something.”

“The situation of violence has been horrible in Mexico,” echoed Archbishop Gustavo Garcia-Siller of San Antonio, Texas. “Sometimes because of fear (the violence) is not named because people are paralyzed. When he says, ‘Unmask the evil,’ it means give a name to the violence.”

Clergy have not escaped the turmoil in Mexico.

By the count of the Catholic Multimedia Center, 1,100 priests reported receiving extortion threats in 2011, while another 255 said they’d received death threats, according to Insight Crime, a website that looks at organized crime in the Americas.

On Saturday evening, after a session with President Felipe Calderon, the pope met with eight victims of Mexico’s rampant violence, among them Maria Guadalupe Davila. Her son was one of 15 youths slain in January 2010 in Ciudad Juarez, gunned down by gang members who mistakenly thought they were members of a rival gang.

The pope leaves for Cuba at mid-morning Monday, marking only the second time the island’s communist leaders have agreed to a visit by a pope. Pope John Paul II spent four days on the island in 1998.