The attack took place on Sunday evening on a busy road leading to the government district, outside a popular cafe.
"It shows the desperation of Al-Shabaab
... the Islamic version of the old Somali warlord...
because they are only hurting innocent civilians," Mohamud said in a statement, updating an initial toll after the blast of four.
In addition, 18 others were maimed, some of them seriously, Mohamud added.
Witnesses said the blast could be heard several streets away.
"I saw charred bodies, I don't know who was targeted but the kaboom was very strong and the site was destroyed," said witness Ahmed Yusuf.
The al-Qaeda-linked Shabaab
...a union consisting of 53 African states, most run by dictators of one flavor or another. The only all-African state not in the AU is Morocco. Established in 2002, the AU is the successor to the Organisation of African Unity (OAU), which was even less successful...
-led troops.
The bombing also came a week after the Shabaab were pushed out of Barawe, the last major port in Somalia that was held by the group and a key source of revenue for the Islamist militia.
Somalia has been riven by civil war since 1991.