Reports of explosions and gunfire at the DusitD2 hotel and offices in Nairobi’s Westlands district surfaced at around 3pm local time (midday GMT).
Eyewitnesses reported seeing four armed men, believed to be militants, throw bombs at vehicles before entering the hotel lobby, the BBC reports.
Images and footage from the scene shows hundreds of people fleeing the complex as gunshots ring out. The hotel says it is closed until further notice.
According to police sources, 15 people were killed, although the Kenyan government is yet to confirm the official toll.