Pope Francis said on Sunday the mistreatment of migrants escaping war and injustice "makes one cry" as he visited the northern Italian city of Turin, stopping to pray before an icon some Christians believe is Jesus' burial cloth.
The Church has not taken an official position, saying the mysterious cloth that has baffled scientists is at least a powerful reminder of Jesus' suffering.
Francis was the latest in a string of popes to pray before the shroud, which is usually kept locked out of sight behind an altar, and is on display for only the third time in 17 years. Hundreds of thousands of people have seen it since the current display began in April.
Francis, born Jorge Mario Bergoglio, is himself of immigrant stock. His grandparents and father emigrated to Argentina from the area around Turin. He was due to meet his Italian relatives on Monday.
In an early-morning address to thousands of workers and unemployed people in a Turin square, he defended the right to employment and urged his listeners, even if they were going through hard times, to reach out to the 10 percent of the city's population living in absolute poverty.
"Immigration increases competition but migrants should not be blamed because they are the victims of injustice, of this throw-away economy, of wars," he said in the manufacturing district that was an engine of Italy's post-war industrial rise.
Departing from his prepared text, he added. "It makes one cry to see the spectacle of these days in which human beings have been treated like merchandise."
Italy's right-wing Northern League, which has won votes from people who say migrants leach resources from a long-stagnant economy, is very strong in the neighbouring Lombardy and Veneto regions.
Francis has made immigration issues a top priority of his papacy. His first trip outside Rome in 2013 was to the southern island of Lampedusa to pay tribute to the thousands of migrants who have died trying to cross the Mediterranean.
France and Austria have stepped up border controls on migrants coming from Italy, turning back hundreds and leaving growing numbers camped out in train stations in Rome and Milan.
The pope later went to the cathedral where he sat in silent veneration before the Shroud of Turin, which bears an image, eerily reversed like a photographic negative, of a man bearing the wounds of a crucifixion.
Measuring 4.4 metres by 1.2 metres, it shows the back and front of a bearded man, his arms crossed on his chest. It is marked by what appear to be rivulets of blood from wounds in the wrists, feet and side.
Carbon dating tests by three laboratories in 1988 caused a sensation by dating it from between 1260 and 1390. Sceptics say it is a masterful medieval forgery but some have challenged the accuracy of those tests.