Afghanistan (searchhas carried out its first execution since the fall of the hardline Taliban (search), putting a bullet in the head of a former military commander convicted of more than 20 murders, officials said Tuesday.

The government did not acknowledge the April 20 execution of Abdullah Shah (searchuntil it was revealed by international human rights group Amnesty International in an e-mailed protest letter Tuesday.

The group assailed the Afghan justice system as "incapable of fulfilling even the most basic standards for fair trials" and called on U.S.-backed President Hamid Karzai (searchto put a stop to capital punishment.

Abdul Mahmood Daqiq, the director of the attorney general's office, confirmed Shah's execution in Pul-e-Charkhi, a jail just east of the capital, and said Karzai's office signed a death warrant for the man.

"Last year three courts confirmed Abdullah Shah's sentence," Daqiq said. "But it was delayed for months until Karzai's office signed off on it."

Daqiq said Shah was shot in the back of the head and that the death sentence was carried out in front of witnesses including representatives of the Afghan police and the Attorney General's office. Doctors were also on hand.