A General Service Unit (GSU) officer on duty at State House, Nairobi, died on Monday after he was attacked with a spear outside Gate D around 11am, prompting heightened security as President William Ruto was inside the compound.

According to officials familiar with the incident, a 56-year-old man approached the checkpoint and stabbed the officer in the chest. Colleagues at the gate subdued the suspect and handed him over to police. The motive of the attack was not immediately clear.

The injured officer--attached to the GSU's G Company--was rushed to Kenyatta National Hospital but was pronounced dead on arrival. His identity is being withheld until the next of kin are informed.

Gate D is commonly used as a public access point during scheduled visits and serves as a security screening area before entry into the State House precincts. Following the incident, officers tightened checks at the perimeter and restricted movement as investigators examined the scene.

Detectives have opened a homicide inquiry and are reviewing witness accounts to establish the suspect's movements before the attack. An autopsy is expected to be conducted to determine the precise cause of death.

Police said further details would be released once preliminary findings are complete.