The blast occurred in Mogadishu’s Hodan district, near two schools and the residence of former president Abdikasim Salat Hassan, according to the Somali National News Agency (SNNA).
Police say the target was an armored vehicle guarding the United Nations, according to SNNA.
The eastern African Somali capital has been rattled by bomb attacks with dozens either killed or injured.
The string of bombings has been linked to notorious terror group Al-Shabaab, which has in the past claimed responsibility for some of the attacks.
Al-Shabaab claimed responsibility for the attack on the facility which was hit twice within a year.
At least one person was killed and 10 wounded in that attack.
Al-Shabaab had earlier claimed responsibility for a bombing at the gate of Mogadishu’s Afrik hotel in January.
The Al-Shabaab Islamist sect was dislodged from Mogadishu in 2011 by local forces with help from the Africa Union, but the terror group has continued to unleash lethal attacks in the city.