Al Qaeda's wing in Yemen blamed a renegade fighter for targeting medics and patients in a military hospital during its attack on the Defence Ministry compound in Sanaa earlier this month, it said in a statement released on Saturday.
"We do not fight in this way, and this not what we call on people to do, and this is not our approach," it said in the statement, adding it had warned its fighters not to attack the hospital.
The killing of unarmed medics and patients, captured on closed-circuit television footage and broadcast by state media, caused widespread outrage in Yemen, where al Qaeda has portrayed itself as fighting for normal people against foreign drone strikes.
Al Qaeda's offshoot Ansar al-Sharia (Partisans of Islamic Law) claimed responsibility earlier this month for the December 5 assault in which at least 52 people were killed, the worst such attack in Yemen for 18 months.
It said it attacked the compound because it believed it to house an operations room for drone attacks carried out by the United States against Islamist militants, which have also led to civilian deaths.
Many of those killed died inside the compound's hospital, where staff said they had seen foreign doctors and nurses executed by attackers.
The footage released on state television showed uniformed figures wandering around the hospital's corridors and wards shooting medics and patients.
One attacker was shown walking up to a group of cowering patients and calmly tossing a hand grenade into their midst before ducking behind a wall.