Al-Qaeda in the Arabian Peninsula (AQAP) has confirmed that Ibrahim al-Rubaish, its top ideological leader and mufti (interpreter of Islamic law), was killed in a US drone strike in Yemen.
The Saudi-born cleric was held in Guantanamo then escaped after repatriation to Saudi Arabia in 2006. He was killed in a "crusade raid" with several other militants, according to a AQAP statement.
The US had offered $5m (£3.4m) for information about his whereabouts.
"He's the biggest name figure that I'm aware of within al-Qaeda's core who's been taken out recently," Robert McFadden, senior vice president of the Soufan Group, told IBTimes UK.
"For someone like him to be killed now, at the very least it takes away from Iranians or those who feel that the US is supporting terrorism.
"There's some chatter out there, somewhere between rumours and official statements, claiming that the US has pulled off its foot off the gas pedal when it comes to al-Qaeda because al-Qaeda represents a foul to the United States' foul in the Houthis and the Iranians."
Saudi-led air strikes targeted the Iran-allied Houthi rebel militia in Yemen after they closed in on the government in exile of President Abd-Rabbu Hadi in Aden, forcing him to leave the Gulf country.
The US set up a "joint planning cell" with Saudi Arabia to provide logistical and intelligence support to the raids.
The Houthis had spread fast from their traditional tribesland in northern Yemen, taking Sana'a in January this year.