Police killed in car bomb explosion
A car bomb has exploded outside a police station in central Nairobi and killed four people, Kenyan police said.
David Kimaiya, the inspector general of police, said two officers are among the dead from tonight's explosion.
A reporter at the scene said it appeared that the blast ripped apart the back end of a sedan.
The blast happened near a police station's main gate.
Terror warnings have been a constant in Kenya in recent months, particularly after September's attack on Westgate Mall killed at least 67 people.
Most of the small-scale attacks and explosions are blamed on al Shabab, the militant group in Somalia that has vowed revenge attacks in Kenya because Kenyan troops moved into southern Somalia in 2011.