The Shabaab militant group claimed responsibility for the blasts in the town of Galkayo, some 700 kilometers (440 miles) northeast of Mogadishu.
“There were two car bomb blasts which targeted the local government headquarters. More than 10 people have been killed,” said police officer Mohamed Abdiqani.
Local resident Hassan Abdukadir said he counted a dozen bodies, some burned beyond recognition.
“It was horrible. The first blast was caused by a truck loaded with explosives, and the second was a minibus,” he said.
Shabaab said it carried out the attack, in a message distributed via the Telegram messaging service, claiming “at least 30 people, including military personnel and apostates were killed.”
The Shabaab carries out regular attacks against government, military and civilian targets using suicide car bombers and gunmen.
In March, Shabaab militants attacked a hotel in Galkayo killing at six people including a senior local government official.
An Al-Qaeda aligned group, the Shabaab is fighting to overthrow the internationally-backed government in the capital Mogadishu and it is expected to try and violently disrupt elections due to be held in September and October.
The Shabaab was forced out of the capital by African Union soldiers five years ago but continues to launch regular attacks including, in recent months, on restaurants, hotels and military bases.
The jihadists have also staged repeated attacks in neighbouring Kenya and a recent security analysis warned the group was expanding its horizons with cells active in Djibouti, Ethiopia, Kenya, Tanzania and Uganda as well as Somalia.