A former Guantanamo Bay prisoner, who had joined al-Qaida after his release, was killed by a U.S. drone strike in Yemen, the group said in a statement Tuesday.

Ibrahim al-Rubaish had fought in Afghanistan before being arrested and held in Guantanamo. He would go on to be one of the top leaders in al-Qaida in Yemen.

The drone attack is a sign that the United States has not abandoned its military campaign against al-Qaida despite the chaos in Yemen. U.S. and Yemeni officials did not immediately comment.

Al-Qaida in Yemen, formally known as "al-Qaida in the Arabian Peninsula," or AQAP, announced the death in a lengthy statement translated by the SITE Intelligence Group. The statement described the drone hit, which it said had taken place two days earlier, as a "hate-filled Crusader strike."

AQAP's statement did not say where the attack took place. But Reuters reported Monday that an unidentified al-Qaida leader was killed near the port city of Mukalla on the Arabian Sea, apparently in a drone strike.

Foreign Policy said that Rubaish was released from Guantanamo in 2006 and sent to Saudi Arabia, where he was placed in a program designed to rehabilitate jihadis.

As NPR's Deborah Amos reported recently, the Saudis say they have a success rate of about 80 percent but acknowledge that about 20 percent of those in the program eventually return to extremist groups such as al-Qaida.

Rubaish joined al-Qaida in Yemen, where, according to The Associated Press:

"He was considered the group's the main ideologue and theological adviser and his writings and sermons were prominent in its publications. Last year, he hailed the seizure of swaths of land in Iraq and Syria by al-Qaida's rival, the Islamic State group."

The U.S. and Yemen have cooperated closely for years in the battle against al-Qaida in Yemen. The U.S. has carried out a sustained campaign of drone strikes against the group, widely considered the most dangerous of the al-Qaida affiliates.

Houthi rebels in January took over Yemen's capital, Sanaa, and forced out President Abed-Rabbo Mansour Hadi, who has taken refuge in neighboring Saudi Arabia.

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