WASHINGTON (CNN) -- A Kuwaiti man released from U.S. custody at the Guantanamo Bay Naval Base in 2005 blew himself up in a suicide attack in Iraq last month, Pentagon officials said Wednesday.

This photo of Abdullah Saleh al-Ajmi was posted on a jihadist Web site.

Abdullah Saleh al-Ajmi was one of two Kuwaitis who took part in a suicide attack in Mosul on April 26, the officials said. Records show that an attack in Mosul that day targeted an Iraqi police patrol and left six people dead, including two police officers.

An announcement on a jihadist Web site earlier this month declared that al-Ajmi was one of the "heroes" who carried out the Mosul operation. A second man from Kuwait also took part in the suicide attack, the Web site said.

Pentagon officials who had been keeping track of al-Ajmi said they were aware he had left Kuwait for Syria, a launching ground for terrorists into Iraq.

A video posted on various jihadist Web sites shows a number of images of al-Ajmi, followed by text reading, "May God have mercy on you Abdullah al-Ajmi. I send you a warm greeting O you martyr, O you hero, O you, a man in a time where only few men are left."

U.S. military records of Guantanamo detainees indicate that a man with the same name and nationality was held at the Cuban prison.

Those records said al-Ajmi, 29, was picked up in Afghanistan as he tried to enter Pakistan after the 2001 U.S. invasion. He claimed to have fought for the Taliban, the records show, and said he fought in a number of battles against the Northern Alliance. Watch a firefight in Afghanistan »

Though he was never charged with any crime, al-Ajmi was held at Guantanamo through 2005. Military documents show he later claimed that his statements about fighting for the Taliban were made after he was threatened while in U.S. custody. He asserted that he was in Afghanistan to study the Quran.

Al-Ajmi was transferred to the custody of Kuwaiti authorities in November 2005, with four other Kuwaitis, and was released after a trial there, according to Pentagon officials.

Al-Ajmi is not the first former Guantanamo detainee to reportedly return to the battlefield after being released. Pentagon officials say there are more than 10 people once held by the U.S. at Guantanamo who have been killed or captured in fighting after being released from the detention facility.

"Our reports indicate that a number of former [Guantanamo Bay] detainees have taken part in anti-coalition militant activities after leaving U.S. detention. Some have subsequently been killed in combat," said Cmdr. Jeff Gordon, a Pentagon spokesman.

Documents provided by the Pentagon show other former detainees returning to the battlefield, including Abdullah Mahsud, who was released from Guantanamo in 2004. He returned to Afghanistan, where he became a militant leader in the Mahsud tribe in southern Waziristan, the documents said.

"We have since discovered that he had been associated with the Taliban since his teen years and has been described as an al Qaeda-linked facilitator.

"In mid-October 2004, Mahsud directed the kidnapping of two Chinese engineers in Pakistan. During rescue operations by Pakistani forces, a kidnapper shot one of the hostages. Five of the kidnappers were killed. Mahsud was not among them," the documents provided by the Pentagon said.

"As these facts illustrate, there is an implied future risk to U.S. and allied interests with every detainee who is released or transferred from Guantanamo," Gordon said.

Reports of former detainees returning to the battlefield show they are dedicated to their cause and have been trained to be deceptive, the Pentagon officials said, but such factors will not prevent the release of other detainees from Guantanamo Bay.

Of the more than 500 detainees released from Guantanamo since the detention camp was opened in 2002, 38 have been stripped of their "enemy combatant" status and determined to pose no future threat to the United States. The remaining 462 were repatriated to home countries or resettled to third-party countries and still considered a threat, Pentagon records show.

Some countries have since released those detainees back into the public, according to various reports.

The United States is still holding about 65 detainees scheduled to be released to their home governments. But before that can happen, the United States has to get assurances the detainees will not be persecuted or harmed when they arrive home, Pentagon officials have said.

"We have no desire to be the world's jailer, which is why the 500 were allowed to depart," Gordon said.

There are about 270 detainees still held at the U.S. prison camp in Cuba.

All About Guantanamo Bay • War and Conflict • Iraq • Afghanistan