The three men had died on the spot and the fourth in hospital.
According to Nur Adan, a police officer, the four killed had recently been appointed by the Somali government to the local administration of the village of El-Baraf, 130km north of Mogadishu.
Meanwhile, a journalist with Shabelle, one of Mogadishu’s main radio stations, who was arrested on Friday, was still in custody early Saturday, according to Jafar Kukay, the station’s assistant director.
The journalist was arrested during a raid on the station by security forces, who ordered it off the air and detained seven members of staff.
Kukay had said that they had accused the radio station of putting out an inaccurate report on violence in Mogadishu the day before.
All the other employees have since been released and the radio has resumed its programming.
It is the third time since January that a radio station in Mogadishu has been raided by the authorities.
Somalia has experienced continued instability despite dozens of peace initiatives since the overthrow of Siad Barre, former president, in 1991.