OKLAHOMA CITY (CNS) -- Archbishop Paul S. Coakley has asked Catholics to offer prayer and penance to prevent a Satanic group from holding a "black mass" Sept. 21 at the Civic Center Music Hall in Oklahoma City.

"Even though tickets are being sold for this event as if it were merely some sort of dark entertainment, this Satanic ritual is deadly serious. It is a blasphemous and obscene inversion of the Catholic Mass," said the Oklahoma City archbishop.

"Using a consecrated host obtained illicitly from a Catholic church and desecrating it in the vilest ways imaginable, the practitioners offer it in sacrifice to Satan," he said. "This terrible sacrilege is a deliberate attack on the Catholic Mass as well as the foundational beliefs of all Christians."

Archbishop Coakley made the comments in an Aug. 4 letter to priests and parishioners throughout the archdiocese. A copy of the letter was released to media Aug. 5.

He said that despite "repeated requests, there has been no indication that the city intends to prevent this event from taking place" and he called on "all Catholics of the Archdiocese of Oklahoma City to counteract this challenge to faith and decency through prayer and penance."

"I have raised my concerns with city officials and pointed out how deeply offensive this proposed sacrilegious act is to Christians and especially to the more than 250,000 Catholics who live in Oklahoma," he added.

"I am certainly concerned about the misuse of a publicly supported facility for an event which has no other purpose than mocking the Catholic faith," he said.

Archbishop Coakley called for a united campaign of prayer, procession and benediction in response to the "black mass." He specifically asked that the prayer to St. Michael the Archangel be included at the conclusion of every Mass from the feast of the Transfiguration of the Lord, which was Aug. 6, and continue through the feast of the Archangels, Sept. 29.

"I invite all Catholics to pray daily for divine protection through the intercession of this heavenly patron who once defeated Lucifer in his rebellion against the Almighty and who stands ready to assist us in this hour of need," he said.

The archbishop also asked parishes in his archdiocese to hold a eucharistic Holy Hour with Benediction between Aug. 15, the feast of the Assumption, and Sept. 21.

He also encouraged parishioners Mayor Mick Cornett "to express your outrage over this offensive and blasphemous sacrilege and this misuse of a tax-supported public space."

Archbishop Coakley invited "all Catholics, Christians and people of good will" to join him for Holy Hour, an outdoor eucharistic procession and Benediction the afternoon of Sept. 21 at St. Francis of Assisi Church in Oklahoma City.

On "the day of the proposed sacrilege," he said, "we will pray to avert this sacrilege and publicly manifest our faith in the Lord and our loving gratitude for the gift of the holy Eucharist, the source and summit of our lives."

Across the country in Massachusetts, a Harvard University student group's plan to conduct a satanic ritual "black mass" on campus in May brought a public outcry, which led to its formal cancellation and an apparently impromptu off-campus version of the event, as well as a well-attended alternative Catholic holy hour.

The planned event had drawn wide criticism from religious leaders, including, Boston Cardinal Sean P. O'Malley, as well as students, alumni and faculty at Harvard.