Zawahiri's death piled pressure on the group to choose a strategic leader who can carefully plan deadly operations and run a jihadi network, experts on al Qaeda say.
The department’s Rewards for Justice programme is offering up to $10 million for information on Adel, whom it says is a member of "al Qaeda’s leadership council” and heads the organisation’s military committee.
He and other Al Qaeda leaders were placed under house arrest in April 2003 by Iran, which released him and four others in exchange for an Iranian diplomat who was kidnapped in Yemen.
OPERATIVE TO LEADERAdel, one of the few remaining al Qaeda old guard, has been close to the central command for decades, experts say.
Adel gained more jihadi credentials after he joined other Arab militants fighting Soviet occupation troops in Afghanistan, where he eventually headed a training camp before becoming a senior figure in al Qaeda.