A gun range owner in Arkansas has received threats and criticism from human rights groups after banning Muslims.

Jan Morgan instituted the ban five months ago at Gun Cave Indoor Firing Range, and continues to defend her decision. 

"We are dealing in lethal firearms," she told FoxNews.com. "I'm not going to let a Nazi shoot in here, or a Ku Klux Klan member in here, either."

Morgan decided to ban Muslims after becoming suspicious of two customers in September. She was disturbed by what she interpreted as suspicious behaviour, and their "Allahu Akhbar" ringtone.

Now, she refuses service to those she thinks are Muslim, based on their last name. A Hindu man said he and his father were erroneously denied service based on their appearance. 

"My dad and I just got kicked out of a Muslim-free gun range," he tweeted last week. "I'm not Muslim, I'm just brown."

The Council on American-Islamic Relations (CAIR) reported Morgan's policy to Attorney General Eric Holder in October, and asked the Justice Department to investigate. 

"Given the recent spike in anti-Muslim rhetoric, including Islamophobic statements by government officials, community leaders and media outlets, death threats, and other bias incidents targeting Muslims, I urge you to investigate this matter soon," the letter read. 

"CAIR believes that systematically banning Muslims from a place of business is a violation of federal laws prohibiting racial and religious discrimination and will inevitably result in a hostile environment for ordinary Muslims in Arkansas."

The Justice Department has not responded to CAIR's letter, and the American Civil Liberties Union of Arkansas reported that no citizens have filed a complaint with them. 

Meanwhile, Morgan says business has quadrupled, and some have offered her donations to fight any future lawsuits. She likened her gun range to the cases of Christian businesses refusing service to gays. 

"One mistake can cost another human being's life," she said. "There's no room for mistakes when you're handling firearms. We aren't just refusing to make a wedding cake here."