Pope Francis has strongly defended refugees at his Christmas Eve mass, urging the world not to ignore the plight of people who are "driven from their land" because of leaders willing to shed "innocent blood".The leader of the world's 1.2 billion Roman Catholics on Sunday led a solemn ceremony for about 10,000 people in St. Peter's Basilica in the Vatican, while many others followed the service from the square outside.In his homily, Francis likened refugees to Mary and Joseph finding no place to stay in Bethlehem and said faith demands that foreigners be welcomed."So many other footsteps are hidden in the footsteps of Joseph and Mary," said the Argentine pontiff, himself the grandson of Italian migrants."We see the tracks of entire families forced to set out in our own day. We see the tracks of millions of persons who do not choose to go away, but driven from their land, leave behind their dear ones."Many engulfed in the ongoing migration crisis were forced to flee from leaders "who, to impose their power and increase their wealth, see no problem in shedding innocent blood", said the 81-year-old.'Herods of today'Wearing white vestments in the flower-bedecked church, Francis called for a "new social imagination ... in which none have to feel that there is no room for them on this earth".Francis has made defence of migrants a major plank of his papacy, often putting him at odds with politicians.The pope also condemned human traffickers who make money off desperate refugees as the "Herods of today" with blood on their hands, a reference to the Biblical story of the king who ordered the killing of all newborn male children near Bethlehem because he feared Jesus would one day displace him.More than 14,000 people have died trying to make the perilous crossing of the Mediterranean to Europe in the past four years.On Christmas Day on Monday, Francis is set to deliver at noon the traditional Urbi et Orbi (to the city and to the world) message and blessings from the central balcony of the Vatican basilica.