LOS ANGELES (AFP) - A US man who allegedly beheaded a female co-worker has been charged with first degree murder and will likely face the death penalty, a prosecutor said on Tuesday, giving details of the grisly attack.

Alton Nolen, 30, spoke in Arabic while he decapitated his victim with a "large kitchen knife," Cleveland County District Attorney Greg Mashburn said, adding that the suspect appeared to hate white people.

Prosecutors have yet to decide whether to seek the death penalty, Mashburn said, adding however that it was "highly likely". The FBI will decide separately whether to bring terrorism charges, he said.

"Obviously there was some sort of infatuation with beheading," he told reporters. "Other than that it seemed to be an isolated incident."

The attack came in the wake of a series of beheadings of Western captives by militant fighters in the Middle East and Algeria, but US officials have not confirmed any link to the Oklahoma case. Nolen had recently converted to Islam.

It occurred last Thursday at a food processing plant in the city of Moore, Oklahoma, where Nolen had just been suspended from his job. He went home and retrieved a kitchen knife, then returned to the front of the company building, where he killed 54-year-old Colleen Hufford, a co-worker.

"Upon entering the building he came across Mrs Hufford and attacked her from behind, ultimately killing her and beheading her," said the prosecutor.

Nolen then attacked another female co-worker - at which point several other people tried to distract him.

"There were multiple attempts by multiple people to stop this attack," said the prosecutor. He was eventually brought down by a company boss, Mark Vaughan, a reserve deputy sheriff who shot Nolen.

Asked what triggered the incident, Mashburn said Nolen had been suspended earlier in the day as a result of a dispute over race.

"From my understanding there was an altercation about him not liking white people," he said. Earlier reports had said he had tried to convert co-workers to Islam.

Nolen, who was injured, remains in hospital but will be arraigned on charges of first degree murder and assault as soon as he is able to leave and be taken into normal custody.

Asked if he could face terrorism charges, the prosecutor said: "There is not a terrorism statute in the state of Oklahoma. If there is, if that avenue is decided to be pursued it could be something that's pursued by the federal authorities."

Prosecutors will discuss whether to seek the death penalty with the victim's family. "That decision is not fair to make without consulting them first but that's highly likely at this point," he said.

His mother broke her silence at the weekend, apologising in a video posted online. "My heart is just so heavy right now," his mother Joyce Nolen said in the video posted Saturday on Facebook. "That's not my son."

On Facebook, Nolen went by the monicker Jah'Keem Yisrael. He posted photographs of the World Trade Centre towers going up in smoke during the September 11, 2001 attacks and of graves.

"THE ONES WHO DIED IN SIN WILL REMAIN IN THEIR GRAVES CAUSE THEIR ALREADY IN HELL!!!" he wrote on September 17 in a posting that got five "likes".

The Islamic Society of Greater Oklahoma City has stressed that "this unwarranted act does not represent Islam in any shape or form".

In a separate case, a Kenyan man is being held on terror charges in nearby Oklahoma City for allegedly threatening to behead a woman days before last week's decapitation in Moore.

Jacob Muriithi allegedly made the threat and mentioned the ISIS (Islamic State4 in Iraq and Syria) extremist group responsible for beheading two American and one British civilian in videos distributed on the internet to a woman working at a nursing home in Oklahoma City, though the woman initially thought he was joking.