VATICAN CITY — Pope Francis on Thursday issued a strong condemnation of modern society’s vices as he urged the faithful to “act soberly” and show compassion in a Christmas Eve Mass in St. Peter’s Basilica.

Thousands of people attended the service, one of the grandest in Catholic Church liturgy. The 79-year-old Francis, who said he was suffering from the flu at the start of the week, sounded slightly hoarse and did not appear to have fully recovered.

“In a society so often intoxicated by consumerism and hedonism, wealth and extravagance, appearances and narcissism, (Jesus) calls us to act soberly, in other words, in a way that is simple, balanced, consistent, capable of seeing and doing what is essential,” he said in his homily.

Criticizing “a world which all too often is merciless to the sinner and lenient to the sin,” and “a culture of indifference which not infrequently turns ruthless,” Francis said “our lifestyle should instead be devout, filled with empathy, compassion and mercy.”

Following tradition, the leader of the world’s 1.2 billion Catholics entered St. Peter’s holding a ferula – a silver papal stick with a cross – and preceded by a procession of cardinals and other top prelates.

The service lasted about 90 minutes.

At the start, Francis lifted a cloth covering a baby Jesus figure in a symbolic celebration of his birth, and children from Belgium, Italy, Kenya, the Central African Republic, the Philippines, Sri Lanka, United States and Mexico laid flowers by the shrine.