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Flames snake along a pool of blood-red wax as Argentine pilgrims place wine and candles where legend says the cowboy and folk saint Gauchito Gil was killed.

Tens of thousands of Argentines are paying homage to Antonio "Gauchito" Gil this week, standing for hours in suffocating heat in an annual pilgrimage to leave offerings at his shrine, thank him for the miracles he has provided - and ask for more.

Gil is famed as a local Robin Hood who lived as an outlaw in the 1800s after refusing to fight in the military in a civil conflict. He is revered for sharing his spoils with the poor and protecting them to this day.

Andrea Ibarra, 26, kneeled before a statue of the popular saint, her shoulders shaking as she pleaded for his help to finish her university studies.

"I get depressed and I need to seek refuge in him to find the strength to continue," said Ibarra, who vowed to join the pilgrimage every year if he helped her.

While many believers in Gauchito Gil are Catholics, the Roman Catholic Church does not recognise him as a saint and church leaders are divided on whether to embrace or condemn the phenomenon.

Legend has it that just before a police sergeant slit his throat, Gil told him he was killing an innocent man who after death could intercede on his behalf with God.

Gil told his executioner to pray to him for his child's recovery from an illness. The sergeant did so and the child was cured, giving birth to the cult of Gauchito Gil.

Tens of thousands of Argentines travel long distances to the town of Mercedes every year around January 8, crowding the roadside sanctuary about 780km north of Buenos Aires.

Revellers dance to accordion music in a celebration that mixes mysticism and drunkenness.

Gil is revered by truckers and bus drivers who believe he protects travellers. Crimson banners on roads all over Argentina mark shrines to him. The words "Thanks, Gauchito Gil" are painted on trucks.

Some roughnecks think he also looks out for bandits.

Juan Angel Zapata has travelled to the rural pocket of northeastern Argentina since he was 8 years old. His mother had prayed to Gil that Zapata be cured of a sickness and he later recovered.

Many of those who worship Gauchito Gil are Roman Catholics careful to distinguish between the miracle-working cowboy and officially recognised saints.

"Because the church did not evangelise enough by telling the faithful their intermediary with God is Jesus, people sought out intermediaries closer to them and to their reality," said Julian Zini, a priest who visits Gil's sanctuary.

He said the church should affirm people's faith but guide it away from superstition and back to Jesus Christ.