In his Christmas Eve homily Thursday, Pope Francis noted the simplicity of Jesus' birth as he rebuked what he called societies' intoxication with consumerism, pleasure, abundance and wealth.

Christians around the world joyfully prepared to recall the birth of Jesus. But in his only public Christmas Mass, in the splendor of St. Peter's Basilica, the pope counter-weighted his joy with a lament for people's excesses and what he described as a "culture of indifference, which not infrequently turns ruthless."

Francis said 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."

Referring to Jesus' birth in a Bethlehem stable, the pope said the child was "born into the poverty of this world; there was no room in the inn for him and his family."

Francis also sounded a cry to right injustices. "In a world which all too often is merciless to the sinner and lenient to the sin, we need to cultivate a strong sense of justice," he said.

Since being elected pope in 2013, Francis has tried to shape the church into one marked more by loving mercy than rigid judgment. He insists that the needs of the poor and others, including refugees and migrants, be paramount.

Youngsters from countries that Francis has visited as pontiff, including Sri Lanka, the Philippines, the United States and most recently, three African nations, left floral bouquets around a baby Jesus statue near the central altar after Francis unveiled and gently kissed the statue.

A child from Mexico, which the pope visits in February, was also among the bouquet bearers.

On Friday, tens of thousands of people are expected to crowd into St. Peter's Square to hear the traditional Christmas day speech, which in the past has been used to denounce wars, other violence and injustice across the globe.