Said al-Shihri, described as the second-in-command of al-Qaeda in the Arabian Peninsula (AQAP), has been killed in an operation in southern Yemen, government officials say.Al-Shihri was reportedly killed with six others in the Hadramawt area.
A Yemeni government website said al-Shihri was a Saudi national who was released by the US from detention in Guantanamo Bay in 2007.
The army has been fighting Islamic militants in the south for months.
The Yemeni ministry of defence website said al-Shihri was killed along with six other militants in an operation, but gave no further details.
Official sources in Yemen told the BBC the death occurred in an air raid in the Wadi Ain area of Hadramawt.
Military sources, however, said it had no information on the death and refused to confirm it. But the sources did confirm that the area was subject to air raids.
Separate Yemeni sources said another Saudi and an Iraqi national were among the other people killed in the operation, which took place last Wednesday.
Yemeni defence ministry officials told Associated Press that the six people killed were travelling in a car and that it was hit by a missile believed to have been fired by a US drone, although this has not been confirmed.
The US, which has labelled AQAP as the most dangerous branch of al-Qaeda, has operated drone attacks in the region previously.
Al-Shihri was said to have escaped a US drone attack on 20 September last year on the village of al-Mahfad in Abyan province.
Al-Shihri was released from Guantanamo Bay in 2007 and had been sent to Saudi Arabia for rehabilitation.
AQAP was formed in January 2009 by a merger between two regional offshoots of the international Islamist militant network in Yemen and Saudi Arabia.
It is now led by Nasser Abdul Karim al-Wuhayshi.
The group has claimed responsibility for a number of attacks and has been blamed by US President Barack Obama for attempting to blow up a US passenger jet as it flew into Detroit in December 2009.
Southern Yemen has been the scene of major clashes between militants and government forces.
The militants took advantage of the uprising that ousted President Ali Abdullah Saleh in February to take control of large parts of the area.