Initial reports suggested the attack involved an explosion followed by gunshots. Meanwhile, in the south, children were playing with a mortar shell when it exploded, killing dozens.
Islamist rebels attacked a hotel in Somalia's capital, Mogadishu, on Friday, prompting a confrontation with security officials.
The al-Shabab group targeted the affluent Pearl Beach Hotel at Lido Beach, often frequented by officials.
There was no confirmation of the number of casualties in the attack.
"The security forces rescued many people from the building and the operation is still ongoing," a government statement said.
What do we know about the hotel attack?
Witnesses said they heard gunfire and explosions at the hotel on Lido Beach. Two suicide bombers blew themselves up at the entrance of the hotel, the DPA news agency reported, citing police officer Mohamed Dahir. Gunmen followed, storming the building.
Other hotel guests were also taken hostage, security official Hassan Ali told DPA.
The siege of the hotel continued on Friday evening. The official Somali news agency posted on Twitter photos purportedly showing security personnel extracting civilians.
Yaasin Nur was at the restaurant and told the French news agency AFP it was "full of people as it was recently renovated."
Explosion in the south kills score of children
Elsewhere in Somalia on Friday, a mortar shell exploded near a town in the Lower Shabelle region, killing some 27 individuals, mostly children.
The children were playing with an intact mortar shell which then exploded. Over 50 others were injured.
The unexploded shell was used by Somalia's warring factions, residents said.
"We request the government and aid agencies to clear mines and shells from the area," Abdi Ahmed, deputy district commissioner of Qoryoley, told reporters.
Al-Shabab has been waging a jihadi insurgency against the Somali central government for more than 15 years.
The al-Qaida-linked jihadi group seeks to establish its own rule based on its strict interpretation of Islamic law in the fragile Horn of Africa country.
rmt/sms (AFP, dpa, Reuters)