Somalia's Islamist al Shabaab militants said on Sunday they had executed three of their own members for treason, two of them for guiding U.S. missiles to kill fellow militants.It was the first time al Shabaab, under pressure from African Union, Kenyan and Ethiopian troops as well as U.S. drone strikes, had admitted to killing its own fighters for betrayals.Al Shabaab, which is affiliated with al Qaeda, said last January that a missile launched from a drone had killed Bilal el Berjawi, a Lebanese al Shabaab fighter with a British passport.Another missile killed four foreign militants south of the Somali capital Mogadishu in February, according to an intelligence officer."We have executed two CIA spies who were behind the killing of our great brothers," Sheikh Mohamed Abu Abdallah, al Shabaab's governor for the Lower Shabelle region, told Reuters on Sunday. "We also executed a third fighter who was proved to be a spy for the UK."