Duke University's decision to scrap plans to allow the Muslim call to prayer to emanate from its chapel bell tower raises controversy on campus. (Reuters)

Duke University canceled plans Thursday to begin a weekly Muslim call to prayer from the campus chapel this week, an initiative that had set off debate on social media. A school spokesman and a Duke Muslim leader said that a serious and credible security threat played a role in the decision.

The university had announced that Muslim students would chant the ‘adhan,’ the call to a weekly prayer service, from the Duke University Chapel bell tower each Friday. The sound of the call to prayer in Muslim communities is a standard part of ritual life on Muslims’ main prayer day. Theologically, it reminds Muslims “to worship God and serves as a reminder to serve our brothers and sisters in humanity,” Imam Adeel Zeb, Muslim chaplain at Duke, said in a news release.

But reaction to the story off campus was swift. Some celebrated the decision.

I support the #DukeCalltoPrayer. Because religious inclusivity is more important than xenophobia. — Erin Howett (@EHowett) January 15, 2015

But many strongly opposed it.

Franklin Graham, president of Samaritan’s Purse and the Billy Graham Evangelistic Association, called on donors and alumni to withhold support from Duke until the policy was reversed. The hashtag #boycottduke spread quickly, and many of the reactions on Twitter referred to recent terrorist attacks, and interpreted it as an anti-Christian move.

Graham posted strong words about it on his Facebook page: “As Christianity is being excluded from the public square and followers of Islam are raping, butchering, and beheading Christians, Jews, and anyone who doesn’t submit to their Sharia Islamic law, Duke is promoting this in the name of religious pluralism. I call on the donors and alumni to withhold their support from Duke until this policy is reversed.”

Immediate growing backlash momentum – people to #BoycottDuke – attend #AmericanFlashmob on Duke Campus starting 12:30 on Fri with #airhorns — Rolliby (@rolliby) January 15, 2015

Muslim call to prayer to begin at Duke University. But Jesus isnt welcome @DukeU #boycottDuke — Shannon Catoe (@shannoncatoe) January 14, 2015

Franklin later praised the reversal.

I am glad to hear that @DukeU reversed its decision to allow Muslim call to prayer from its chapel bell tower. They made the right decision! — Franklin Graham (@Franklin_Graham) January 15, 2015

In discussing the change Thursday, Duke officials said the response to the decision was not what the university had expected.

“Duke remains committed to fostering an inclusive, tolerant and welcoming campus for all of its students,” said Michael Schoenfeld, vice president for public affairs and government relations, in a news release. “However, it was clear that what was conceived as an effort to unify was not having the intended effect.”

Schoenfeld said Thursday night that a “serious and credible” security threat was one of the reasons for the decision. University officials declined to elaborate.

Omid Safi, director of Duke’s Islamic Studies Center, said Thursday evening that the call to prayer was scaled back because of “a number of credible threats against Muslim students, faculty and staff.” The school, he said “is treating this as a criminal matter” and that the threats are “external.”

Muslim students, Safi said, have been advised not to speak and be identified, “and are scared and disappointed.” Asked if he personally had been threatened, he said he had been advised by officials to say “a number of credible threats have been made.”

On Friday, he said, there would still be a new addition to the weekly service: A call to prayer, but it would be from the steps of the chapel instead of amplified from the tower. The initial decision to have a call, he said, came last semester upon the urging of the Office of Religious Life – the overall chaplains’ office with clergy from various faiths – and Muslim students, together. He said Duke is considered a leader in Islamic studies and hospitable for Muslims. More than 100 people show up each Friday for prayer, he said.

“We had hoped for a symbolic action that would shine a light on how a leading international university in the American South can be a place where the symbol of the Christian heritage of the university is demonstrating hospitality to its Muslim community members. And instead we’re having to talk about crazy people,” Safi said.

When the idea of holding the call from the tower was pitched, he said, no one thought it would be a problem. He blamed “geography” and Duke’s proximity to influential evangelical leader Franklin Graham, son of Billy Graham.

“Duke has been committed to Islamic studies for decades,” he said.

The university has held the weekly jummah prayers in the basement of Duke Chapel for many years, starting with the traditional chanted call to prayer. More than 700 of the 15,000 students at Duke identify as Muslim, according to school officials.

Duke today is non-sectarian but has historic and symbolic ties with The United Methodist Church. Its bylaws were recast last year to say its purposes are grounded in the Christian tradition of intellectual inquiry and service to the world. Sapp described the chapel as “a church.”

On Wednesday, a Duke dean of religious life published an essay in the News & Observer touting the decision to hold the call, a common sound in Muslim communities around the world.

“This opportunity represents a larger commitment to religious pluralism that is at the heart of Duke’s mission and connects the university to national trends in religious accommodation,” wrote Christy Lohr Sapp, associate dean for religious life at Duke University.

In her essay, Sapp noted that “there is much negative press” today touching Muslims, “from ISIS to Boko Haram to al-Qaida.” The call, she wrote, would be the antithesis, and “might help students feel more at home in a world marred by weekly acts of violence and daily discriminations. Perhaps, too, this small token of welcome will provide a platform for a truer voice to resonate: a voice that challenges media stereotypes of Muslims, a voice of wisdom, a voice prayer and a voice of peace.”

Now Muslim students and others on campus wishing to take part in the prayer will meet on the quadrangle outside the Chapel before gathering in the Chapel for prayers.

“Our Muslim community enriches the university in countless ways,” Schoenfeld said. “We welcome the active expression of their faith tradition, and all others, in ways that are meaningful and visible.”

President Obama said Friday that United States' "one big advantage" against terrorism was the feeling of belonging that American Muslims have to the country. He said some Muslims in European countries did not have these same national ties. (AP)

This story has been updated.