Explosions in the Kenyan capital of Nairobi have killed at least three people.

Officials say they believe the blasts came from grenades hurled at a crowd at a bus station. More than 20 people are injured.

This is the latest in a string of grenade attacks on the capital since Kenya sent troops into Somalia in October to fight al Qaida-aligned al-Shabab militants.

Police arrested a man shortly after the attack who claimed to be an al-Shabab member.