The death of Al-Qaeda in the Arabian Peninsula's second-in-command, Saeed al-Shehri, has dealt a severe blow to what Washington considers the global jihadist franchise's deadliest branch, analysts say.
Yemen said on Thursday that Shehri, a Saudi national and former Guantanamo Bay detainee, was killed in a November 28 counter-terrorism operation in the northern province of Saada.
"Saeed al-Shehri's death deals a blow to AQAP, which he was effectively in charge of," said Mustafa al-Ani, director of the Gulf Research Center for security and terrorism issues.
Nasser al-Wuhayshi, a Yemeni, is the official head of AQAP, which was born of the fusion in 2009 of Al-Qaeda's Saudi and Yemeni branches, after a successful Saudi campaign to clamp down on the group's activities in the kingdom.
But "Shehri was the group's operational commander. He was a man of action who planned and oversaw AQAP's operations in Yemen, Saudi Arabia and elsewhere in the world," Ani said.
"His loss is even more important than that of Osama bin Laden," Al-Qaeda's top leader who was killed in May 2011 in a US special forces raid on his hideout in Pakistan.
Bin Laden had been isolated to maintain his own security before he was killed, with some experts saying his operational effectiveness as head of the global network was reduced as a result.
Yemen's operation against Shehri was carried out "in cooperation with the international fight against terrorism" on November 28, the Supreme National Security Committee said in Thursday's statement.
The United States has stepped up its ongoing campaign of drone strikes against suspected Al-Qaeda targets in the Arabian Peninsula country, carrying out 53 in 2012 compared to the previous year's 18.
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Washington says the Yemeni branch is the most active and deadliest in Al-Qaeda, and the only one that poses a real threat to the US on home soil.
"AQAP planned the failed attack by Nigerian jihadist Umar Farouk Abdulmutallab on a Christmas Day 2009 Amsterdam-Detroit flight," and also claimed a November 2010 attempt to detonate bombs hidden in printer cartridges aboard cargo planes travelling to the US, Ani said.
"Shehri's death was announced at the beginning of this week by members of his family who were informed via telephone by an AQAP member," he said, adding that the group would likely officially confirm his killing within days.
Shehri's shoes will be hard to fill.
"A Saudi might well replace him, but it'll be difficult to find a successor with the same military experience," said Ani. "Around 50 to 70 Saudi extremists are currently in Yemeni territory."
Yemeni Al-Qaeda specialist Saeed Obeid al-Jimhi, said "the Saudi Arabian explosives expert Ibrahim al-Assiri, who masterminded the printer cartridge attacks, could succeed Shehri."
Assiri is also the brother of Abdullah al-Assiri, an AQAP suicide bomber who in August 2009 tried to assassinate Saudi royal and anti-terrorism chief Prince Mohammed bin Nayef bin Abdel Aziz by setting off a bomb hidden inside his own body.
And AQAP are currently under intense military pressure.
"The hunt for AQAP's leaders in Yemen will intensify, since Shehri's elimination was thanks to an infiltration of the group by its enemies," Jimhi said.
"In fact, it's possible that AQAP head Nasser al-Wuhayshi has already been killed or seriously injured because there's been no sign of him (in the group's propaganda) for more than a year."