The attacks happened in the southern region of Lower Shabelle on bases in the towns of Awdheegle and Bariire -- some 30 kilometres (17 miles) apart. Both are forward operating bases in the fight against the Islamist group.

"The assailants tried to attack but thanks to our brave soldiers who knew about the tricks of the assailants, the militants were defeated and their wounded and dead bodies are strewn around, we will provide you the details later," army chief General Odowa Yusuf Rage told reporters.

"The forces are still pursuing the rest of the attackers and the Somali army is in control of the both contested locations."

Witnesses in Awdheegle -- home to the larger of the two bases -- said Somali troops had repelled the militants after around an hour of heavy fighting.

"Shabaab gunmen used a vehicle loaded with explosives to launch the attack, but they failed to enter the camp after nearly an hour of exchanging machine gun fire with the Somali troops," town resident Mohamed Ali said by phone.

"I saw several dead bodies of the Shabab gunmen near the camp where the fighting occurred, the Somali soldiers paraded these bodies after the fighting."

In Bariire, a car bomb was also detonated before heavily armed gunmen stormed the base.

"We heard a heavy explosion caused by a suicide bomber ramming a car at the entrance to the base and a heavy exchange of gunfire followed," said resident Abdirahim Malin.

"A few minutes later the militant fighters managed to enter the camp and torched some military supplies belonging to the Somali army."

Al-Shabaab, which has been waging a long insurgency to unseat the internationally backed government in Mogadishu, claimed responsiblity for the attack in a statement on a pro-Shabaab website.

The group claimed it had killed dozens and captured military vehicles and supplies.

Casualties are often difficult to establish from Al-Shabaab attacks in remote areas, especially when the military is targeted.

Al-Shabaab were driven out of Mogadishu in 2011, but still control swathes of territory from where they plan and launch frequent, deadly strikes against government and civilian targets.