SAN QUENTIN: California prison officials executed Stanley Tookie Williams, the ex-leader of the Crips gang who brutally killed four people in 1979, early on Tuesday after Gov. Arnold Schwarzenegger and top courts rejected appeals to spare his life.

The time of death was 12:35 a.m. PST (0835 GMT) Tuesday.

Some 2,000 opponents of the death penalty gathered outside the gates of San Quentin, where civil rights leader Rev. Jesse Jackson addressed the crowd and folk singer Joan Baez sang spirituals.

The execution by lethal injection at San Quentin State Prison north of San Francisco followed a frenzied but failed effort to reopen the case by supporters of Williams, 51, who repudiated gang life during his 24 years on death row.

The case generated fierce debate over the death penalty in the United States because Williams has written a series of books warning young people against gangs.

Witnesses said guards struggled for about 12 minutes to place the needle in a vein in his left arm, frustrating Williams who occasionally spoke with the guards preparing his death, asking at one point: "Still can't find it?"

After he was strapped down, he raised his head often, especially to look at Barbara Becnel, the editor of his books and foremost supporter who helped bring broad publicity to his case. After his death, Becnel and two other supporters broke the silence in the witness room, saying: "The state of California just killed an innocent man."

A relative of one of the victims wept as the prisoner's supporters made their defiant statement.

Becnel and other supporters said Williams' anti-gang work showed the inmate had changed fundamentally in the half of his life he has spent in prison. But Schwarzenegger and others said his continued protestations of innocence negated any claim that he had redeemed himself.

"Stanley Williams insists he is innocent, and that he will not and should not apologize or otherwise atone for the murders of the four victims in this case," Schwarzenegger wrote on Monday in denying clemency.

"Without an apology and atonement for these senseless and brutal killings there can be no redemption."

"Based on the cumulative weight of the evidence, there is no reason to second guess the jury's decision of guilt or raise significant doubts or serious reservations about Williams' convictions and death sentence."

Jackson said he broke the news on Monday afternoon that Schwarzenegger had denied clemency as Williams met several supporters in prison.

"He said 'Don't cry, let's remain strong,'" Jackson told Reuters. "He smiled, you know, with a certain strength, a certain resolve."

"I think he feels a comfort in his new legacy as a social transformer," Jackson said.

"I am not the kind of person to sit around and worry about being executed," Williams told Reuters last month. "I have faith and if it doesn't go my way, it doesn't go my way."

Williams was convicted in 1981 of killing Albert Owens as he lay face down on the floor of a 7-Eleven convenience store in a $120 robbery. Two weeks later, Williams shot dead an elderly Taiwanese immigrant couple running a motel, as well as their visiting daughter.

At the Vatican, Pope Benedict's advisor for justice issues, Cardinal Renato Martino, condemned the execution and called the death penalty "the negation of human dignity."

Prison officials said Williams was composed and cooperative and said he did not request a final meal after eating oatmeal and drinking milk earlier in the day.

Among the throng gathered outside the prison was Christina Williams, 23, who said: "I wanted to show them we oppose the death penalty even if you are a murderer." She held hands with her two young children and wore a "Save Tookie" button on his jacket. "He changed his life and deserves a second chance."

The nation's top courts disagreed.

On Monday, the U.S. Supreme Court as well as the 9th Circuit Court of Appeals rejected final appeals to reconsider the case.- Reuters