WASHINGTON (CNN) -- A federal judge ordered the release of five Guantanamo Bay detainees Thursday, saying the government failed to show that they were "enemy combatants."

A guard keeps watch from a tower at the military facility at Guantanamo Bay, Cuba.

Judge Richard Leon issued the order in the case of six detainees who were challenging their detention.

The ruling by a Bush administration-appointed judge represented another legal setback for the government on detainee policy.

The Justice Department said it "disagrees with the Court's decision" but did not announce whether it would appeal the order.

The six men listened by phone from Guantanamo to Leon's ruling as an interpreter in Washington interpreted it phrase-by-phrase in Arabic. Their end was on "mute," and their reaction was not heard.

In June, the Supreme Court court ruled that all detainees at Guantanamo were entitled to challenge their continued detention.

On Thursday, Leon ruled that five of the six should be released because the government failed to show by a preponderance of evidence that any of them, other than one man identified as bin Saeed, had planned to travel to Afghanistan to take up arms against the United States and its allies, as the government claimed.

Claims by a single source against five of the men brought up questions of credibility, reliability and corroboration, the judge said.

He ruled, however, that the government had provided ample evidence against the sixth man to prove that he was "an al Qaeda facilitator."

That detainee is identified in government documents both as Bensayah Belkacem or Belkacem Bensayah. Leon referred to him as "Mr. Bensayah."

All six men are Algerians who were arrested in Bosnia in 2002. Initially, the U.S. government claimed that they were suspects in a plot to blow up the U.S. Embassy in Sarajevo.

They were flown to Guantanamo Bay, and five years later, the U.S. government dropped the embassy bombing allegations. But U.S. officials said the men were planning to go to Afghanistan to fight against the U.S. and coalition troops there.

Leon, whom President Bush nominated to the federal bench a day before the September 11 terrorist attacks, said he recognized that the government could appeal but issued an unusual caution.

"I, too, have a right to appeal to the Justice Department, the FBI, the CIA and the Department of Defense," Leon said. "My appeal to you is to strongly urge that you take a hard look at the evidence, both presented and lacking, as to these five detainees" before pursuing an appeal.

Justice Department chief spokesman Peter Carr said the government was pleased with the Bensayah ruling.

"We are promptly reviewing the decision with respect to the other five petitioners," Carr said. "We are of course disappointed by and disagree with the Court's decision that we did not carry our burden of proof with respect to the other detainees."

As many as 200 other Guantanamo detainees are challenging their detentions in cases pending in federal courts.

About 250 detainees remain at Guantanamo, down from a peak of roughly 750 men from 40 countries.

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