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A snarling pit bull came to the defense of his drugged-out owner who was fighting with another junkie Friday morning at a luxury high-rise in Midtown, police said.

The dog attacked his owner’s antagonist and left him with a bunch of bite wounds and scratches on the ninth floor of The Biltmore on W. 47th near Eighth Ave. just before 9 a.m., fire officials said.

The canine’s owner argued bitterly with a 27-year-old man at the ritzy building and then they got physical before the dog jumped into the fray.

The combatants trashed Apartment 9J, and the bitten man left smears of blood on the apartment floor, on the outside of a closet, and on the walls of the hallway five feet off the floor. Belts were strewn across the floor and an overturned painting by the front door had bloodstains on it.

“I heard a man screaming. He was screaming so bad I thought he was mentally ill,” said a woman who lives on the hall and declined to give her name.

“The police told us to stay in our apartments. I didn’t know if it was a hostage situation or a bomb threat.” Anthony DelMundo/New York Daily News The owner of the pit bull was arrested and taken to Bellevue Hospital.

The woman said she has noticed the pit bull before the mauling. “He’s aggressive,” she said. “When he’s waiting for the elevator, I go back in my apartment.”

Gilles Grenier, 58, has lived in the apartment building for 14 years. “I remember hearing loud screams,” Grenier said.

“I reported that dog when they moved in. Pit bulls are just killing machines. They’re not animals. They need to be muzzled.”

Cops called in the heavily armed Emergency Service Unit, which broke up the fight, restrained the pooch, and took it to the city Center for Animal Care and Control.

Both Walsh and the second man were arrested — Walsh escorted out by an ESU cop armed with a submachine gun — and taken by separate ambulances to Bellevue Hospital. They have not been formally charged.

“They were both heavily on drugs,” a police source said.

Walsh’s lawyer, David Cohen, said Walsh and the dog were close. With Jefferson Siegel, Shayna Jacobs