Pope Francis urged the world to "roll up our sleeves" for peace in a New Year's message Saturday, telling the faithful to keep positive while working to build a better society.

Marking the 55th World Day of Peace, the head of the world's 1.3 billion Catholics devoted his Angelus address to encouraging a stop to violence around the world, telling the assembled crowd at Saint Peter's Square to keep peace at the forefront of their thoughts.

"Let's go home thinking peace, peace, peace. We need peace," said the pope, following his Angelus prayer.

"I was looking at the images in the television programme ‘In His Image’ today, about war, displaced people, the miseries. This is happening today in the world. We want peace."

Under sunny skies, the pope -- who turned 85 on December 17 -- reminded the faithful that peace required "concrete actions," such as forgiving others and promoting justice.

"And it needs a positive outlook as well, one that always sees, in the Church as well as in society, not the evil that divides us, but the good that unites us!" he said, speaking from the window of the Apostolic Palace.

"Getting depressed or complaining is useless. We need to roll up our sleeves to build peace."

Earlier Saturday, during mass in Saint Peter's Basilica in honour of the Virgin Mary, Francis delivered a homily in which he called violence against women an insult to God.

"The Church is mother, the Church is woman. And since mothers bestow life and women 'keep' the world, let us all make greater efforts to promote mothers and to protect women," he said.

"How much violence is directed against women! Enough! To hurt a woman is to insult God, who from a woman took on our humanity."

On New Year's Eve, Pope Francis did not preside over vespers at St Peter's Basilica as planned, instead turning the service over to the dean of the College of Cardinals, Giovanni Battista Re, the dean of the College of Cardinals.