The pope called for respect of all people without discrimination and the protection of children from war and violence today as he celebrated the start of the new year.

The first day of the year is also the Roman Catholic church's World Day of Peace, and the pontiff issued an appeal to all armed groups to "stop, reflect and abandon the way of violence", even if it seems impossible.

"You will feel in your hearts the joy of peace, which you have perhaps long forgotten," he said during the Angelus prayer.

He said peace began by recognising that men were brothers, not rivals or enemies.

"Peace begins with a look of respect that recognises in another man's face a person, regardless of the colour of his skin, nationality, language or religion," he said during a mass in St Peter's Basilica.

The value of respect for all should be taught from an early age, he said. Noting that classes containing children of different backgrounds were common, he said that "their faces are a prophecy of the kind of humanity we are called upon to create: a family of families and peoples."

The 82-year-old put children, especially those hurt by conflict or forced to leave their homes, at the heart of his call for peace.

He said they made it evident that men were brothers because "despite differences, they cry and laugh the same way, have the same needs, communicate spontaneously, play together".

The painful images of children at the mercy of war and violence, their faces "disfigured by pain and desperation," were a silent appeal for peace, he said.

The pope celebrated the mass a week after he was knocked down by a woman on Christmas Eve. He was unhurt in the fall and has kept up his busy holiday schedule.

In his comments, Benedict also renewed his call to protect the environment, saying that the degradation of man leads to the degradation of the planet.