The dead include Americans, Kenyans, a Brit and Tanzanians.
"The operation is over," police officer Major Mohamed Abdi told Reuters by telephone from Kismayu.
Members of the al-Qaeda linked group stormed the hotel after targeting it with a car bomb on Friday while local elders and lawmakers were meeting to discuss approaching regional elections.
The police have said that all attackers are dead.
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.
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.