Pope Francis has greeted several thousand migrants, including many asylum-seekers, in St. Peter's Square, encouraging them to hang on to hope.

Many refugees were waving flags of their countries when Francis addressed them during his traditional Sunday appearance to faithful in the square as the Catholic church worldwide marked a day dedicated to refugees.

Francis told them: "Each of you carry in yourselves a history, a culture, precious values" along with experiences of poverty, oppression and fear.

The pope says: "don't let anyone rob you of this hope and the joy for life."

Europe is struggling to shelter or integrate hundreds of thousands of people who have been fleeing war, persecution and poverty. Some Europeans are worried about rising crime and the costs of hosting migrants.