somalia islamist al shabaab insurgency shoot four men accuse spy monday public execution underscore insurgents control swathe country southern region even government gird offensive four men capture weeks ago publicly execute today court rule admit espionage mohamed abu abdalla al shabaab governor jubba regions say phone two spy ethiopian government two spy somali government intelligence men shoot buale capital middle jubba say region mostly control al shabaab lie south capital mogadishu government return call seek comment al shabaab grip horn african nation weaken since push capital 2011 african union peacekeepers still control large part countryside try overthrow weak u.n.-backed government impose strict form islamic law somalia rive civil war since 1991 clan warlords overthrow dictator turn somalia 's islamist insurgency execute four men accuse spy