Kenyan television featured appeals for blood from local hospitals.
Kenyan police chief Joseph Boinnet said a suicide bomber had been involved in the attack.
The incident, involving several explosions and an exchange of gunfire, began earlier in the afternoon in the Westland district of the capital, which also houses a bank and a number of offices. Local television showed smoke rising from a compound in the district of the city.
Special forces have cordoned off the area with reports of people still trapped inside the hotel. While Nairobi police commander Philip Ndolo reported it could possibly be a robbery, police spokesperson Charles Owino told AFP that a terrorist attack couldn’t be ruled out.
“All police teams, including anti-terror officers, have been dispatched to the scene. As of now, we are treating it as anything, including the highest attack,” said Owino.
Gunmen blasted their way into the hotel and office complex, sending workers fleeing for their lives as others cowered under their desks. Police warned the “terror attack” may still be ongoing, with the assailants still inside the upscale 14 Riverside Drive complex.
“The main door of the hotel was blown open and there was a human arm in the street, severed from the shoulder,” said Serge Medic, the Swiss owner of a security company, who ran to the scene to help civilians when he heard of the attack from his taxi driver.
Medic, who was armed, said he entered the building with a policeman and two soldiers, but they came under fire and retreated.
“One man said he saw two armed men with scarves on their head and bandoliers of bullets,” Medic s aid, as gunfire echoed in the background more than two hours after the attack began.
A woman shot in the leg was carried out and three men emerged, covered in blood. Some office workers climbed out of windows. Many said that they had had to leave colleagues behind, still huddled under their desks.
“There’s a grenade in the bathroom,” one officer yelled as police rushed out from one building.
“We heard a loud bang from inside. Then I saw shattered glass,” said Geoffrey Otieno, who works at a beauty salon in the complex. “We hid until we were rescued.”
Kenya has often been targeted by al-Shabaab, which killed dozens of people in a shopping centre in 2013 and nearly 150 students at a university in 2015.
“We are behind the attack in Nairobi. The operation is going on,” said Abdiasis Abu Musab, the group’s military operations spokesperson.
According to its website, 14 Riverside is home to the offices of international companies including BASF, Colgate Palmolive, Reckitt Benckiser, Pernod Ricard, Dow Chemical and SAP, as well as the dusitD2 hotel, part of the Thai hotel group Dusit Thani.
The Australian embassy is across the road from the compound.
Al-Shabaab says its attacks in Kenya are revenge for Kenyan troops stationed inside Somalia, which has been riven by civil war since 1991.
The Kenyan troops, concentrated in the south, originally went into Somalia to try create a buffer zone along the border. They are now part of an AU peacekeeping force supporting the weak UN-backed c entral government. African News Agency (ANA) Reuters