WASHINGTON, Jan 13 (Reuters) - The Pentagon said on Tuesday that 61 former detainees from its military prison at Guantanamo Bay, Cuba, appear to have returned to terrorism since their release from custody.

Pentagon spokesman Geoff Morrell said 18 former detainees are confirmed and 43 suspected of "returning to the fight."

He said the figures, updated at the end of December, showed a higher rate of recidivism than seen in a previous report showing 37 former detainees as active militants.

He provided no details about the detainees or their countries of origin.

"The overall known terrorist re-engagement rate has increased to 11 percent" from about 7 percent, Morrell said.

The numbers were generated by the Pentagon's Defense Intelligence Agency based on fingerprints, photographs and intelligence reports, he said.

President-elect Barack Obama, who takes office on Tuesday, is expected to issue an executive order to close the Guantanamo Bay prison, possibly within his first week in office.

About 255 men are still held at the U.S.-run naval base in Cuba, a symbol of aggressive interrogation methods that exposed the United States to allegations of torture.

Washington has cleared 50 of the detainees for release but cannot return them to their home countries because of the risk they would be tortured or persecuted there.

Around 500 others have been freed or transferred to other governments since 2002.

Pentagon officials say scores of detainees still in custody should never be released because of the potential danger they pose to U.S. interests. (Reporting by Andrew Gray and David Morgan)

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