Al Shabaab militants killed at least 18 civilians and destroyed trucks laden with relief food in an overnight attack in Somalia's central region, residents and a state news agency said on Saturday, News.az reports citing Reuters.

The Islamist group launched the attack in the Hiran area in the semi-autonomous state of Hirshabelle in central Somalia. The trucks were transporting food supplies from Baladweyne city to Mahas town, residents said.

"Al Shabaab killed 18 civilians and burnt...several trucks of relief food heading to Mahas town last night," Farah Aden, a local elder told Reuters by phone.

State news agency Sonna reported that al Shabaab fighters had burnt trucks carrying relief food to Mahas and "killed most of the people on board the vehicles."

The al Qaeda-linked Islamist group has been battling Somalia's central government for more than a decade. It wants to establish its own rule based on a strict interpretation of Islamic sharia law.