Bin Laden
Somalia-based al Qaeda operatives were suspected in two suicide attacks in neighboring Kenya that killed 224 people at the US embassy in 1998 and 15 at an Israeli-owned beach hotel in 2002.
Security and intelligence sources say Ayro, who has been in hiding since surviving a US air strike in January 2007, trained in Afghanistan in the late 1990s.
He was one of six members or associates of al Qaeda thought by the United States to be in Somalia.
In late February, Washington officially listed the Shabaab as a terrorist organization, saying it had close ties to Osama bin Laden's network.
The al Shabaab is the militant wing of the Somalia Islamic Courts Council that took over most of southern Somalia for the second half of 2006, until the government and Ethiopian forces routed it in a two-week war.
Under Ayro, the Shabaab adopted Iraq-style tactics, including assassinations and roadside bombs and claimed at least one suicide bombing -- unheard of in Somalia's moderate Sufi Islamic customs.
Western security officials and diplomats say it has also been responsible for killing aid workers and journalists, the desecration of an Italian colonial-era cemetery in 2005 and scores of attacks during the insurgency.
In rare taped comments released in November, Ayro ordered his fighters to attack a small African Union peacekeeping force based in Mogadishu.