In the Internet statement, Al Qaeda in Yemen identified its new deputy leader as Abu Sayyaf al-Shihri, saying he returned from Guantánamo to his native Saudi Arabia and then traveled to Yemen “more than 10 months ago.” That corresponds roughly to the return of Mr. Shihri, a Saudi who was released from Guantánamo in November 2007. Abu Sayyaf is a nom de guerre, commonly used by jihadists in place of their real name or first name.

A Saudi security official, speaking on the condition of anonymity, said Mr. Shihri had disappeared from his home in Saudi Arabia last year after finishing the rehabilitation program.

A Yemeni journalist who interviewed Al Qaeda’s leaders in Yemen last year, Abdulela Shaya, confirmed Thursday that the deputy leader was indeed Mr. Shihri, the former Guantánamo detainee. Mr. Shaya, in a phone interview, said Mr. Shihri had described to him his journey from Cuba to Yemen and supplied his Guantánamo detention number, 372. That is the correct number, Pentagon documents show.

“It seems certain from all the sources we have that this is the same individual who was released from Guantánamo in 2007,” said Gregory Johnsen, a terrorism analyst and the editor of a forthcoming book, “Islam and Insurgency in Yemen.”

Mr. Shihri, 35, trained in urban warfare tactics at a camp north of Kabul, Afghanistan, according to documents released by the Pentagon as part of his Guantánamo dossier. Two weeks after the terrorist attacks of Sept. 11, 2001, he traveled to Afghanistan via Bahrain and Pakistan, and he later told American investigators that his intention was to do relief work, the documents say. He was wounded in an airstrike and spent a month and a half recovering in a hospital in Pakistan.

The documents state that Mr. Shihri met with a group of “extremists” in Iran and helped them get into Afghanistan. They also say he was accused of trying to arrange the assassination of a writer, in accordance with a fatwa, or religious order, issued by an extremist cleric.

However, under a heading describing reasons for Mr. Shihri’s possible release from Guantánamo, the documents say he claimed that he traveled to Iran “to purchase carpets for his store” in Saudi Arabia. They also say that he denied knowledge of any terrorists or terrorist activities, and that he “related that if released, he would like to return to Riyadh, Saudi Arabia, wherein he would reunite with his family.”