Gunmen have attacked an hotel in Kenya’s capital,

Gunmen have attacked an upscale hotel and office complex in Kenya’s capital, causing an unknown number of casualties.

The attack at the Dusit D2 Hotel in Nairobi began around 3:30 pm Tuesday afternoon. Witnesses reported hearing at least one explosion and sustained gunfire.

Kenyan news organizations say several people were killed in the attack. There has been no confirmation from authorities.

Somalia-based militant group al-Shabab has claimed responsibility for the attack, according to VOA’s Somali service. The group later released a second statement saying “fierce clashes” continued at the site.