Adult film star Christy Mack takes to social media to show the horrific injuries she allegedly suffered at the hands of ex-boyfriend, MMA fighter 'War Machine'. Courtesy Fox 5 News

FUGITIVE mixed martial arts fighter War Machine has been arrested in California on suspicion of beating his ex-girlfriend so severely in Las Vegas that she feared for her life.

Police have released the mugshot of the 32-year-old fighter and former porn actor, whose birth name is Jon Koppenhaver, after he was captured in the Los Angeles suburb of Simi Valley.

The MMA fighter sitting in the hotel room with a pizza and a small amount of cash,” TMZ reported and had been fully co-operating with police.

He currently remains behind bars.

Authorities issued a warrant for Koppenhaver on Monday, the same day his ex-girlfriend, adult film actor Christy Mack, posted graphic photos of her swollen, beaten face online.

Added below are the graphic photos and story about what happened pic.twitter.com/U1T1X2OP4d — Christy Mack (@ChristyMack) August 11, 2014

Mack said in a statement that Koppenhaver showed up unannounced at her house on August 8, found her and a friend unarmed, and beat the friend without uttering a word.

Koppenhaver then sent the friend away and turned to Mack, forcing her to shower before knocking out some of her teeth and breaking bones in her face, the statement said.

She wrote that she feared for her life as he sawed off her hair with a dull knife.

“He made me undress and shower in front of him, then dragged me out and beat my face. I have no recollection of how many times I was hit, I just know my injuries that resulted from my beating. My injuries include 18 broken bones around my eyes, my nose is broken in 2 places, I am missing teeth and several more are broken,” she said. “After some time, the knife broke off of the handle and continued to threaten me with the blade. I believed I was going to die. He has beaten me many times before, but never this badly. He took my phone and cancelled all of my plans for the following week to make sure no one would worry about my whereabouts.

“I ran out my back door, shutting it behind me so the dogs didn’t run inside to tip him off. I hoped the fence to the golf course behind my house and ran to a neighbouring house. Naked and afraid he would catch me, I kept running through the neighbourhood knocking on doors. Finally one answered and I was brought to the hospital and treated for my injuries,” she said.

Koppenhaver had been abusive in the past and broke up with her in May, she said.

“After many months of fear and pressure to keep this man happy, I feel that I can no longer put myself in this situation,” Mack wrote.

Koppenhaver tweeted a response to the attack while he was on the run.

“@ChristyMack I love you and hope you’re okay. I came him (sic) early to surprise you and help you set up for your convention. I can’t believe what I found and can’t believe what happened,” he wrote. “I’m so heart broken ... in all ways. I will always love you.”

Koppenhaver did not return a message on Tuesday seeking comment about Mack’s account, and it’s not clear whether he has an attorney.

The welterweight fighter made his Ultimate Fighting Championship debut in 2007. He lost his only pay-per-view bout in 2008 and went on to fight for a variety of promotions over the past five years.

His criminal record includes a 2012 conviction for attempt to commit battery with substantial bodily harm.

US marshals said they worked with police and Department of Homeland Security agents to capture Koppenhaver. He was booked into the Simi Valley Jail while awaiting extradition to Nevada.

“This is yet another example of how our joint agency efforts are apprehending fugitives who think they can hide,” District of Nevada US Marshal Christopher Hoye said in a statement.