There was no immediate claim as to who was responsible for the blast.
"Security forces have entered a small portion of the hotel building. the exchange of gunfire is hellish", he said.
Police officer Major Abdullahi Aden told Reuters the auto bomb said: 'They are fighting inside.
Two of the five attackers were killed on the first floor, Hussein said.
According to Somali national news agency (SONNA), former MP Abdinasir Garane and former police commissioner of Daynile district Mohamed Yusuf were among the dead.
Islamist group al-Shabab, responsible for scores of such attacks in the country's long civil war, said it carried out Saturday's bombings.
The first explosion was reportedly caused by a auto bomb.
"The Mujahedeen fighters are inside Nasa Hablod 2 hotel where... apostate officials are staying", said a brief statement posted on a pro-Shabaab website, quoting Andalus.
"We targeted ministers and security officials who were inside the hotel".
Saturday's explosions occurred two weeks after an enormous blast in Mogadishu that killed at least 358 people.
A suicide auto bomb first detonated after being rammed into the gates of Hotel Nasa Hablod Two, which is close to the presidential palace.
Its sister hotel, the Nasahablod, was targeted by Al Shabab in a similar attack that killed 11 people in June a year ago.
Al-Shabab often targets high-profile areas of Mogadishu.
A 22,000-strong multinational African Union force in Somalia is expected to withdraw its forces and hand over the country's security to the Somali military by the end of 2020. US military officials and others in recent months have expressed concern that Somali forces are not yet ready.
The US military also has stepped up military efforts against al Shabab this year in Somalia, carrying out almost 20 drone strikes, as the global war on extremism moves deeper into the African continent.