Her skull-face peers from beneath a cloak, the Grim Reaper's scythe often clutched in her hand. She is the Saint of Death, icon of an underground cult that for many years has been the bane of the Roman Catholic Church and Mexican governments.

It is a cult that has grown exponentially in the last decade, in part as a reaction to rising violence across the country. Seen as a form of protection, La Santa Muerte has come to be cherished by the "other side" of Mexico — the marginalized, impoverished and sometimes-criminal sector that lives by hook, crook or wily, informal enterprise. Drug-traffickers are among her biggest fans.

And so the arrest this week of one of the leading promoters of the Santa Muerte "church" seemed both surprising and inevitable.

David Romo, a self-appointed bishop of the church, stands accused of running a kidnapping ring and laundering its ransoms through his personal bank account.

Mexico City prosecutors Tuesday paraded Romo and three women and four men detained with him before television cameras as they read out charges. Romo broke protocol and shouted that he had been tortured and that his arrest was politically motivated, as several of the female suspects wept.

To bolster their case, prosecutors released videotape from security cameras at a bank that purportedly showed Romo withdrawing some of his ill-gotten gains.

His supporters rallied angrily to his defense, saying officials were attempting to persecute and discredit their faith. Several experts said that regardless of Romo's guilt or innocence, however, his promotion of a form of worship on the edges of mainstream society put him at loggerheads with authorities.

Romo, who often appeared wearing a priest's collar, has also been accused by other proponents of Santa Muerte of placing too much emphasis on commercialization of the practice.

"It's these kinds of stories that give Santa Muerte a bad reputation," said Eva Aridjis, a Mexican documentary maker whose film "La Santa Muerte" was released in 2007.

Santa Muerte ritual mixes elements of pre-Columbian indigenous practices and African customs with elements of Catholicism and has flourished as Mexico has become a more dangerous place amid a deadly drug war and economic crisis. Many today find it a refuge, a more accepting form of worship freed from the strict rules of formal Catholicism. Traffickers and prison gangs ask La Santa Muerte for her protection as they commit their crimes.

The formal church condemns the cult, saying it exalts a figure of death. La Santa Muerte is not a recognized saint, nor is Romo a recognized bishop.

Bernardo Barranco, an expert on religions who writes for the Mexican newspaper La Jornada, said some Catholic Church leaders have come to see La Santa Muerte as a threat because it has attracted so many followers. In 2005, the government's Interior Ministry yanked the group's official recognition as a religious organization.

The heart of Santa Muerte worship is in the tough Mexico City neighborhood of Tepito, home to a notorious black market and where scores of altars have been erected with images of the cloaked, skeletal figure. It is also where Romo based his practice.

Romo's supporters are calling for demonstrations outside the government detention center where he is being held.

"La Santa Muerte will not abandon the father, and nor will we," said one supporter in an Internet message. "This is war."