One of the most debated pieces of cloth in the world is back on public display after a five-year hiatus.

Even among Christians, its authenticity as a relic is hotly debated, but in spite of the uncertainty it remains a massive crowd puller. 

After five years away from the public eye, the shroud went back on display on Sunday in the Italian city of Turin. 

And the town is bracing itself for a massive turnout as no fewer than a million people have already booked tickets to see the contested linen, according to the Agence France-Presse news agency.

The Turin Shroud is believed by some to be the burial cloth of Jesus Christ because it shows the faint outline of what appears to be a crucified man.

Tests have dated it to the 13th century but in spite of the evidence leaning away from genuine relic, the shroud continues to hold a tantalizing air of mystery. 

And that appears to be enough to convince over a million people to line up for a glimpse of the cloth between now and June 24.

The slots are free to book but ticketholders will only have a few minutes each to take in the display and make up their own minds about the cloth. 

Among those who will be paying a visit to the Turin Shroud is Pope Francis, who will be in the town from June 20 to 21.  

The last time the shroud went on public display was in 2010, to coincide with the 200th anniversary of the birth of St John Bosco, a monk who spent his life serving Turin's poor. 

During that display, more than two million people came to see the shroud. 

This time round, visitors will also be able to learn more about its history in a companion exhibition. 

While the Catholic Church is responsible for the shroud's preservation, it does not maintain that it is indeed the burial cloth of Jesus Christ. 

"It is not a profession of faith because it is not an object of faith, nor of devotion, but it can help faith," Turin Archbishop Cesare Nosiglia said earlier this week, according to AFP.