The Somali-based militant group al-Shabab claimed the attack but gave no details. Four armed men entered the complex, eyewitnesses say.
People are leaving the site escorted by heavily armed officers. One man was led out with a gunshot wound in the back.
Explosions and gunfire are being reported around a hotel complex in Kenyan capital, Nairobi.
Local television showed smoke rising from the compound in the Westland district of the city, which houses the Dusit hotel as well as offices.
“We are under attack,” a person inside the complex told Reuters news agency.
Several vehicles are on fire in the car park. Police have been sent to the area.
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