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.