NAIROBI, Kenya (AP) — A Kenyan police chief says a blast on a busy street in the capital, Nairobi, has killed at least one person.

Anthony Kibuchi said authorities suspect that the person killed was carrying explosives, but police are still investigating.

The Friday evening blast happened near a military air base, and Kibuchi said authorities will try to determine if the base or military personnel were the intended target.

Downtown Nairobi has seen a series of grenade attacks over the last year, with one such attack killing nine people.

Al-Shabab militants in Somalia have threatened attacks in Kenya, but it's not clear that the small grenade attacks or Friday's blast are from al-Shabab, an al-Qaida-linked insurgent group.

U.S. Secretary of State Hillary Rodham Clinton arrives in Kenya on Saturday on her 11-day tour around Africa during which she is expected to discuss the growing security threat from Islamist militants.