Pope Francis held an open air Mass Sunday for some 300,000 Catholic faithful in Mexico City's gritty suburb of Ecatepec.
The pontiff, in his message, spoke out against the drug trade and associated violence, a central theme of his five-day visit.
"Let's get that in our heads, with the devil there is no dialogue," he said while urging the faithful to resist vanity, pride and wealth.
In a final prayer at the end of the Mass, Francis urged Mexicans to be on the " front lines'' in forging their country's future.
He urged them to make their country "a land of opportunities, where there will be no need to emigrate in order to dream, no need to be exploited in order to work, no need to make the despair and poverty of many the opportunism of a few, a land that will not have to mourn men and women, young people and children who are destroyed at the hands of the dealers of death.''
The city of Ecatepec lies in the populous state of Mexico, a region plagued by warring drug cartels and infamous for a spate of disappearances of women, whose bodies have turned up in abandoned lots or canals.
According to the National Citizens Observatory on Femicide [murders of women], in 2011 and 2012, nearly 1,300 girls and women -- more than half between the ages of 10 and 17 -- disappeared in Mexico, while 448 were murdered, many with gruesome violence. Further data shows that only about one-in-four such cases are investigated, with less than 2 percent of those leading to arrests and convictions.
On Saturday, the Pope called on Mexican leaders to provide "true justice" and security in the country after years of endemic drug violence, official corruption and poverty.
Francis told President Enrique Peña Nieto and assembled lawmakers in Mexico City they have a responsibility to help citizens gain access to "indispensable material and spiritual goods," including housing, employment and a peaceful environment."
In a separate address to Mexican bishops, Francis urged the clerics to take a more aggressive stand against drug trafficking and corruption. He challenged church leaders to denounce what he called the "insidious threat" posed by trafficking.
On Monday, the pope travels to Chiapas, Mexico's poorest state, where he will preside over a Mass conducted in three indigenous languages. He then visits Morelia, the capital of the western state of Michoacan, where farmers in 2013 took up arms to battle the so-called Knights Templar drug cartel.
Francis caps his visit Wednesday in the U.S.-Mexican border city of Ciudad Juarez, Mexico's former murder capital, where he is expected to address issues of crime, trafficking and migration.