* Attacks show rebels still have power in capital
* Most of those beheaded were teenage boys
MOGADISHU, Aug 26 (Reuters) - Somalia's Islamist al Shabaab militants beheaded at least two young boys in Mogadishu, an activist said on Friday, in the latest of a string of attacks showing they still had the power to strike despite a well publicised withdrawal.
At least seven other youths were reported beheaded in the city in recent weeks, Fartun Abdisalan of the Elman rights group told Reuters.
The outgunned and divided rebel force pulled its fighters out of bases in parts of Mogadishu earlier this month, after waging a four-year insurgency against government and African Union troops.
Analysts said it was only a matter of time before the militants regrouped and re-emerged in Mogadishu, as a guerrilla fighting force.
Residents told Reuters al Shabaab militanta had started broadcasting messages across the city, using mosques' loundspeaker systems, urging followers to behead spies and other enemies.
"We understand they (al Shabaab) want to engage in guerrilla fighting and the beheading is just to shock residents so that no one turns against them," Abdisalan said.
"Two beheaded bodies of young boys were thrown in the former spaghetti factory building and in the livestock market yesterday (Thursday)," she told Reuters.
A 19-year-old man from the village of Garas Baleylat, 13 km (8 miles) northwest of Mogadishu, was found beheaded on Thursday, said one of his relatives.
"Al Shabaab beheaded my cousin, Qadar Omar Siyad, yesterday. For the past few days, the group has been announcing beheadings in mosques in the city. They even said most Muslims in mosques are infidels," Mohammed Siyad told Reuters.
Siyad said masked men grabbed his cousin on Wednesday, bundled him into a vehicle and drove towards north Mogadishu's Daynile district, where al Shabaab has been putting up resistance.
"On Thursday, his beheaded body was found lying in the livestock market. His hands and legs were bound together, his front teeth were missing and his lower lip was cut," Siyad told Reuters.
Al Shabaab follow an austere version of Sharia Law and they frequently carry out beheadings and amputations in the areas they control in much of south and central Somalia.
Thousands of Somalis have been returning to Mogadishu since the rebels' withdrawal, rebuilding their homes and businesses, in the hope the lull in violence would hold.
"Everyone is shocked here and the only question is who will be beheaded next," Siyad said.
On Friday evening, a car bomb parked near the busy K-5 area, exploded and wounded one pedestrian, witnesses said. (Reporting by Abdi Sheikh; Writing by Yara Bayoumy)
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