The wife of a man charged with the murder of three young Muslims in North Carolina on Tuesday has denied that the attack was motivated by religion.

Karen Hicks, wife of 46-year-old Craig who handed himself into police, told a news conference yesterday that her husband had been engaged in a long-standing dispute over parking with the victims. Hicks believed "everyone is equal" and "championed the rights of others", she said.

The killings "had nothing do with religion or the victims' faith,"  she added. Last night, she issued a statement noting that she is filing for divorce.

Hicks' victims have been identified as Deah Shaddy Barakat, 23, his 21-year-old wife Yusor Mohammad Abu-Salha and her sister Razan Modammad Abu-Salha, 19.

Gunshots were heard at their home in an apartment complex at the University of North Carolina, Chapel Hill, at around 5.15 pm on February 10.

All three were pronounced dead at the scene, with sources saying they had been shot in the head.

A Facebook page under Hicks' name describes him as an "anti-theist", with Hicks using the page to criticise religion. He apparently regularly posted images with text mocking religious beliefs.

One post, from January 28, reads: "People say nothing can solve the Middle East problem, not mediation, not arms, not financial aid. I say there is something. Atheism."

Another says: "Praying is pointless, useless, narcissistic, arrogant, and lazy; just like the imaginary god you pray to."

The Council on American Islamic Relations (CAIR) has issued a statement calling for the Chapel Hill Police Department to address speculation that the murders were motivated by the victims' Muslim faith.

"Based on the brutal nature of this crime, the past anti-religion statements of the alleged perpetrator, the religious attire of two of the victims, and the rising anti-Muslim rhetoric in American society, we urge state and federal law enforcement authorities to quickly address speculation of a possible bias motive in this case," said CAIR National Executive Director Nihad Awad.

The father of the two murdered women branded the incident a "hate crime".

"This was not a dispute over a parking space; this was a hate crime," Dr Mohammad Abu-Salha told the North Carolina News and Observer.

Hicks had "picked on" Barakat and Yusor, who were recently married, he said. "They were uncomfortable with him, but they did not know he would go this far."

He also blamed the American media for "bombard[ing]" citizens with "Islamic, Islamic, Islamic terrorism and makes people here scared of us and hate us and want us out."

"So if somebody has any conflict with you, and they already hate you, you get a bullet in the head," he told AP.

Tributes have poured in for the young victims, with the hashtag #MuslimLivesMatter trending on Twitter. An estimated 2,000 people attended a candlelight vigil on Wednesday night.

The local police chief has pledged to "exhaust every lead" to determine whether Hicks was motivated by religion.

In a statement, Mayor of Chapel Hill Mark Kleinschmidt said: "We do not know whether anti-Muslim bias played a role in this crime, but I do recognise the fear that members of our community may feel. Chapel Hill is a place for everyone, a place where Muslim lives matter."