Fences are being erected in some countries to keep out migrants and refugees, but this only aids the criminal organisations who traffic human beings, Pope Francis said Wednesday.

"Today, the current economic crisis unfortunately fosters attitudes of closure instead of welcome," Francis told pilgrims at his weekly general audience in St Peter's Square.

"In some parts of the world, walls and barriers are being built. But this actually ends up favouring criminal trafficking," he stated.

The only solution to the phenomenon of migration is solidarity, Francis said.

"Solidarity with the migrant, solidarity with the 'foreigner'. It appears that the silent work of men and women who, in different ways, do what they can to help and assist refugees and migrants, is being drowned out by the noise made by those who give voice to an instinctive egoism."

The growing influx of refugees fleeing war, famine and dire poverty requires Christians to welcome and care for them, as they have done through the ages, said Francis.

"Dioceses, parishes, religious institutes, organisations and individual Christians: we are all called to welcome our brothers and sisters who are fleeing war, hunger, violence and cruel conditions of life.

"As followers of Christ, may we never close our hearts to those in need."