ROME — An Italian priest denied Wednesday that he sexually molested a fellow altar boy when both were teenagers at the Vatican's youth seminary, taking the stand for the first time in a criminal trial over alleged abuse within the Vatican walls.

The Rev. Gabriele Martinelli told the Vatican tribunal that the allegations against him were unfounded and implausible. He said they were the fruit of divisions in the seminary as well as "jealousy" among former seminarians that he was eventually ordained a priest.

The St. Pius X seminary, located in a palazzo inside the Vatican gardens, houses boys aged 12-18 who serve as altar boys at papal Masses in St. Peter's Basilica. The scandal erupted in 2017 when former altar boys went public with allegations of misconduct against Martinelli and cover-up by the seminary superiors.

Martinelli is accused of abusing his authority as a more senior seminarian to force a younger seminarian, identified as L.G., into "carnal acts" of sodomy and masturbation, using violence and threats, from 2007-2012.

Martinelli strongly denied the allegations Wednesday, telling the court that the abuse claims were physically impossible given the layout of the seminary and that the rector could enter the dorm rooms at any time. He denied having any power over the younger altar boys and said the claims were more about discrediting him and the seminary, fueled by people who prefer the old Latin rite liturgy over the Mass in vernacular.

"Talking about abuse, they targeted me but above all they wanted to target the (youth seminary)," he said.

The former seminary rector, the Rev. Enrico Radice, is charged with having helped Martinelli avoid investigators by discrediting L.G.'s allegations as baseless.

At the last hearing, Radice denied he knew anything about any abuse or even sexual behavior at the seminary, saying he did his rounds at night and would have seen or heard something.

"The walls were thin, you could hear everything," he said, adding that he believed the accusers were making their claims for "financial interests."

The scandal is particularly grave because the abuse allegedly occurred within Vatican City itself, and the allegations were known since at least 2012. Some bishops looked into them, but no one ever interviewed the presumed victim, L.G.

After L.G. and his onetime roommate, Kamil Jarzembowski, went public in 2017, Pope Francis waived the statute of limitations, allowing a criminal investigation to proceed.

During Wednesday's hearing, reference was made to a letter L.G. apparently wrote to Francis himself on June 9, 2017.

The scandal erupted publicly five months later with the November, 2017 publication of a book, "Original Sin," recounting Jarzembowski's claims that he witnessed L.G., being molested by Martinelli.