WASHINGTON — An American drone strike has killed a top ideologue and spokesman for Al Qaeda’s branch in Yemen, the terrorist group announced Tuesday. The spokesman, Ibrahim al-Rubeish, a 35-year-old Saudi citizen, had been held for five years in the United States military prison at Guantánamo Bay.

A statement from Al Qaeda in the Arabian Peninsula, posted on Twitter, said that Mr. Rubeish was killed Monday in what it called a “hate-filled Crusader strike” near Al Mukalla, a city on Yemen’s southern coast.

Since 2009, Mr. Rubeish has been the group’s voice in many important pronouncements, including a video eulogy for Anwar al-Awlaki, the American cleric killed in a drone strike in 2011.

Mr. Rubeish, the latest of a half-dozen senior Qaeda operatives killed by American strikes in Yemen over the past year, was drawn into the terrorist network as a young man and rose nearly to the top of Al Qaeda’s most dangerous affiliate. The statement said Mr. Rubeish “spent nearly two decades as a mujahid,” an Islamic fighter, “in the cause of Allah, battling against America and its agents,” according to a translation by the Site Intelligence Group.