Public works minister Abbas Abdullahi Sheikh Siraji was shot dead in his car in the capital Mogadishu in early May.

Soldier Ahmed Abdulahi Ahmed, was condemned to death by a military court "for mistakenly shooting the minister," army officer Hassan Ali Noor told Reuters. A second soldier at the scene at the time was released without charge on Monday.

Siraji, 31, grew up in a Kenyan refugee camp and was the country's youngest minister.

Militants from the al Qaeda-affiliated group al Shabaab have carried out frequent attacks in Mogadishu as they fight to oust Somalia's Western-backed government and drive out African Union peacekeeping troops.

In a separate incident on Monday Abifutah Omar Halane, the spokesman for Mogadishu's mayor, said security agents had arrested on Monday the head of a unit of al Shabaab responsible for assassinations and bombings in the capital, Abdiwahid Khalif Ahmed. The unit is known as Amniyat.

"This is the man who organizes the killing of civilians and suicide attacks in the capital, and we succeeded in capturing him this morning. He was also behind assassinations in the capital that targeted government members," Halane told Reuters.

In the most recent attack last week, al Shabaab fighters killed at least 19 people in a suicide and car bomb attack on a busy hotel and nearby restaurant in Mogadishu.