Pope Francis said on Christmas Eve during Mass in St. Peter's Basilica in Rome that modern society should return to the essential values of life and urged his 1.2 billion followers to have compassion for the less fortunate.

The 10,000 or so in attendance started the service with the Kalenda, a traditional Latin chant proclaiming the birth of Jesus.

The pope urged those "intoxicated" by possessions to return to a more simple life, and said that everyone should allow the simplicity of the child Jesus, who was born in a manger, to inspire their lives.

"In a society so often intoxicated by consumerism and hedonism, wealth and extravagance, appearances and narcissism, this Child calls us to act soberly," he said in his homily to thousands in attendance.

Security at the Basilica was tighter than normal, as many police carried out spot checks and those in attendance had to pass through metal detectors upon entry.

The 79 year-old Argentine Pope, who said he had a slight flu earlier this week, told his followers that they should be "filled with empathy, compassion and mercy" and should "cultivate a strong sense of justice, to discern and to do God's will."

He said further that Christmas was the time to "once more discover who we are." It follows his statement last week that countries should review their laws on refugees and migrants.

On Christmas day, Francis is due to deliver the traditional "Urbi et Orbi" (to the city and the world) message from St. Peter's Square. Tens of thousands are expected in attendance to hear the pontiff deliver his speech.

smm/jm (Reuters, dpa, AFP, AP)