Mohamed al-Zawahiri, brother of al Qaeda leader Ayman al-Zawahiri, will be freed from prison in Egypt after 13 years, his attorney said Monday.

He was acquitted by an Egyptian military court and will be released Tuesday, said attorney Nizar Ghorab.

Mohamed al-Zawahiri was imprisoned in 1999 after being detained and extradited from the United Arab Emirates on allegations that he was linked to the 1981 assassination of Egyptian President Anwar Sadat. Al-Zawahiri was acquitted on the assassination charges but later was accused of conspiring against the Egyptian government.

He was sentenced to death, but then appealed the ruling.