A presidential candidate for upcoming regional elections was also killed in the assault by four militants, Jubbaland president Ahmed Mohamed said in a statement. At least two journalists and a UN agency staff member were also reported to have been killed, Presstv Reported.
Police officer Major Mohamed Abdi earlier told Reuters that security forces had ended the overnight attack.
Takfiri group al-Shabab, which is trying to topple Somalia's central government, on Friday claimed responsibility for the attack, which saw fighters storm the hotel after targeting it with a car bomb while local elders and lawmakers were meeting to discuss the elections.
Regional president Mohamed said that three Kenyans, one Briton, two Americans and three Tanzanians were among those killed.
"Among the dead was also a Jubbaland presidential candidate named Shuuriye. Four militants attacked the hotel. One of them was the suicide car bomber, two were shot dead and one was captured alive by Jubbaland security forces," he said.
He added that 56 people had been wounded in the attack, including two Chinese citizens.
Police had said earlier all the attackers had been killed.
The Somalia office of the UN's International Organization for Migration also said on Twitter one of its local staff members, Abdifatah Mohamed, was among those killed.
SADO Somalia, a local non-governmental organization, also said on Twitter its executive director Abdullahi Isse Abdulle had been killed in the attack.
A journalists' group had confirmed on Friday that two journalists were among the dead; Somali-Canadian journalist Hodan Naleyah, the founder of Integration TV, and Mohamed Sahal Omar, reporter of SBC TV in Kismayu.
Jubbaland president Mohamed said Jama Fariid, Naleyah's husband, had also been killed.
Separately, Mohamed Ibrahim Moalimuu, general secretary of the Federation of Somali Journalists, said in a statement: "We are saddened and outraged by this loss of life, and condemn in the strongest possible terms this appalling massacre."
Al Shabaab was ejected from Mogadishu in 2011 and has since been driven from most of its other strongholds.
It was driven out of Kismayu in 2012. The city's port had been a major source of revenue for the group from taxes, charcoal exports and levies on arms and other illegal imports.
Kismayu is the commercial capital of Jubbaland, a region of southern Somalia still partly controlled by al Shabaab.
Al Shabaab remains a major security threat, with fighters frequently carrying out bombings in Somalia and neighboring Kenya, whose troops form part of the African Union-mandated peacekeeping force that helps defend the Somali government.