By Suzi Parker

LITTLE ROCK, Arkansas (Reuters) - Three men imprisoned for the "satanic" 1993 slayings of three 8-year-old boys in Arkansas walked free on Friday after nearly two decades of proclaiming their innocence from behind bars.

Damien Echols, Jason Baldwin and Jessie Misskelley Jr., known as the "West Memphis Three," took an "Alford plea" in which they could continue to claim their innocence but pleaded guilty in exchange for an 18-year sentence and credit for time served.

Their release came after DNA tests failed to link them to the crime and before an evidentiary hearing due in December to determine if they should receive a new trial.

Teenagers at the time of the killings in the Arkansas-Tennessee border town of West Memphis, Echols, now 37, had been on death row, while Baldwin, 34, and Misskelley, 36, had been serving life sentences.

"As far as the state is concerned, this case is closed," prosecutor Scott Ellington said, adding the plea deal did not amount to an exoneration and that the state still believed the men were guilty. "I strongly believe that the interest of justice was served today."

Despite the guilty pleas, the defendants maintained their innocence in a news conference after the hastily called hearing in Jonesboro, Arkansas, at which they were released. They said they would continue to seek justice for the victims and try to clear their names.

The deal was "not perfect, by any means," Echols said.

"But at least it brings closure to some areas, and in some aspects," he said, sitting beside his wife, Lorri.

"We can still bring up new evidence. We can still continue the investigations we've been doing. We can still continue to clear our names. The only difference is now we're doing it from the outside," he said.

Echols called his time in prison a "living hell."

Police at the time of the murders of Steven Branch, Christopher Byers and James Michael Moore called the killings "satanic" because the children's naked bodies had been bound and mutilated.

DNA TESTS DIDN'T LINK MEN TO CRIME

The West Memphis Three always maintained their innocence in the deaths of the boys, and pressure had been mounting to free the trio.

Recent DNA tests did not link the men to the crime scene and showed the presence of others who have not been identified.

Families of the victims have been split on whether the men were guilty or innocent. They did not speak at the news conference, but Branch's father had to be removed from the courtroom after interrupting proceedings to object to the deal, witnesses said.

John Mark Byers, whose son Christopher was one of the three boys killed, told a local television station: "I'm glad they're free and they can go home to their family. I'm disappointed they have the stain ... of guilt behind their name, because I know they're innocent."

Since the men's 1994 conviction, their cause was championed by activist groups and celebrities such as Pearl Jam frontman Eddie Vedder and Dixie Chicks singer Natalie Maines, both of whom were in Jonesboro for the hearing.

The legal proceeding on Friday protected Arkansas from a potential lawsuit in case the men had won a new trial, been acquitted and sued the state for wrongful imprisonment, Ellington said.

He said the state believed the defendants could easily have been acquitted in a new trial due to the deaths of witnesses, DNA tests, changing stories and stale evidence. But he said the state never questioned the guilty verdicts and that "guilt or innocence was never on the table."

Baldwin initially resisted the deal because he felt it would negate attempts to clear his name, but finally agreed, he said, for the sake of his friend Echols on death row.

"They were trying to kill Damien," he said.

(Writing by Karen Brooks; Editing by Jerry Norton, Cynthia Johnston and Peter Cooney)