Pope Francis has pleaded for peace in a world broken by conflict, terrorism and injustice in which people suffer due to the economic ambitions of the few and because of the "greed and the idolatry of money."

The pontiff was speaking to some 40,000 people gathered in St. Peter's Square during his traditional Christmas Day "Urbi et Orbi" address on Dec. 25

The Pope wished Christmas peace for people scarred by wars and for those who have lost loved ones to terrorism.

He said his message was aimed at "all peoples, especially those scarred by war and harsh conflicts that seem stronger than the yearning for peace."

Francis cited those suffering through the Syrian war, especially during the "most awful battles" in Aleppo urging the international community to find a negotiated solution.

He also urged Israelis and Palestinians to abandon hate and revenge, grieving that in Nigeria "fundamentalist terrorism exploits even children," seen as a reference to child suicide-bombers.

He denounced conflicts and tensions in Africa, eastern Ukraine, Myanmar, the Korean Peninsula, Colombia and Venezuela.

The Pope referred to peace, not merely the word, "but a real and concrete peace – to our abandoned and excluded brothers and sisters, to those who suffer hunger and to all the victims of violence.

"Peace to exiles, migrants and refugees, to all those who in our day are subject to human trafficking.

"Peace to the peoples who suffer because of the economic ambitions of the few, because of the sheer greed and the idolatry of money, which leads to slavery.

"Peace to those affected by social and economic unrest, and to those who endure the consequences of earthquakes or other natural catastrophes."

The night before Francis said Christmas has been "taken hostage" by dazzling materialism that puts God in the shadows and blinds many to the needs of the hungry, the migrants and the war-weary.

Francis was leading the world's 1.2 billion Roman Catholics into Christmas for the fourth time since his election in 2013.

"If we want to celebrate Christmas authentically, we need to contemplate this sign: the fragile simplicity of a small newborn, the meekness of where he lies, the tender affection of the swaddling clothes. God is there," the Pope said at St Peter's Basilica.