NEW YORK (Reuters) - New York City on Tuesday agreed to pay $5.75 million to the mother of a mentally ill black man who died in 2013 after he was found in his cell naked and covered in feces at Rikers Island, court records show.

Bradley Ballard, 39, was locked in his cell at the problem-plagued New York City jail complex and deprived of running water and sufficient insulin for his diabetes for six days leading up to his death on Sept. 11, 2013.

A report issued by the state's Commission of Correction said his condition was also complicated by sepsis, which he developed from mutilating his genitals and not receiving necessary medical care, and listed the death as a homicide.

The report said the medical care, provided by a former contractor that no longer works with the city, as well as prison staff was, "so incompetent and inadequate as to shock the conscience."

New York City Department of Corrections Commissioner Joseph Ponte, whose tenure started after Ballard's death, said in a statement: "Bradley Ballard's death was a tragedy and our hearts go out to his family. We have zero tolerance for the mistreatment of any inmate,"

The city's law department said it did not renew the contract with the medical provider, Corizon Health Inc. Corizon could not be immediately reached for comment on Tuesday night.

The settlement said the city, the Department of Corrections and officials listed as defendants did not admit fault or liability in the case. The case was filed in federal court in Manhattan in September 2014 by Ballard's mother, Beverly Ann Griffin.

"I don't think anyone can recall a case where the abuse and mistreatment was more egregious. This was a total system failure, an astonishing display of inhuman treatment," Griffin's attorney, Jonathan Abady, said in a statement.

Abady said the settlement ranks as the largest such agreement in the city's history, but added: "That provides no consolation. There's no victory or happy ending here."

The settlement came amid continued scrutiny of safety and security at Rikers Island, one of the largest U.S. jail complexes with around 10,000 prisoners daily.

Dozens of guards have been criminally charged in recent years for an array of offenses, including assaulting inmates and smuggling contraband. A guard pleaded guilty earlier this month to charges that he tried to cover up an assault by a fellow officer that led to an inmate's death in 2012.

(Reporting by Nate Raymond in New York; Writing and additional reporting by Curtis Skinner; Editing by Bill Rigby)