Al-Shabab militants have carried out two separate attacks on Somali military bases in the Lower Shabelle region.
The militants used a vehicle laden with explosives to damage a bridge leading to the base at Qoryoley.
An army spokesman told AFP news agency the attack was repelled with the help of AU peacekeepers.
Heavy fighting was reported earlier when al-Shabab fighters attacked another base at El Salini.
The army said the militants had suffered heavy losses. The number of army casualties is not yet known.