The bomber also died in the attack at the Al-Shifa hospital in Mogadishu, said Mohammed Abdi.
Al-Shabab insurgents claimed responsibility for the attack on Twitter saying they were targeting a group of Turkish diplomats. The group said the operation was not a suicide attack and that those who carried out the attack had safely gone back to their bases.
Al-Shabab, which has links with al-Qaida, has been carrying out guerrilla attacks in Somalia since the group was expelled from the capital by African Union troops in August 2011. It has long been threatening Turkish workers and aid agencies in Somalia accusing them of spreading secularism in Somalia.
"The Turkish are part of a group of nations bolstering the apostate regime and attempting to suppress the establishment of Islamic Shari'ah," al-Shabab said on Twitter.
The expulsion of al-Shabab in the capital ended years of daily violence that had caused the rest of the world to shun the capital for two decades. After the ouster of al-Shabab the international community started trickling back into Mogadishu, and the United Nations began moving its personnel to Somalia from Kenya.
But al-Shabab still holds sway in some parts of rural southern Somalia and retains the ability to stage lethal attacks even in Mogadishu.
Earlier this month a bomb exploded inside the largest market in the Somali capital, wounding at least five government soldiers aboard a military vehicle.
The bomb was concealed inside a Somali military pick-up truck in Mogadishu's sprawling Bakara market, Mogadishu police official Mohamed Hussein said.
The United Nations envoy in Somalia condemned the attack. Nicholas Kay, head of the U.N. Assistance Mission in Somalia that began operations last month, offered his condolences to the Turkish government, victims and their families.
"Turkey has been working tirelessly and bravely to help the Somali people over the last few years," he said in a statement.
The U.S. State Department made a similar statement.
"This cowardly act will not shake our commitment to continue working for the brighter, more democratic and prosperous future the people of Somalia deserve," spokeswoman Jen Psaki said.