Interior Ministry spokesman Zemarai Bashari said both police and civilians are among the dead and wounded. A correspondent for RFE/RL's Radio Free Afghanistan quotes officials as saying the death toll could be higher.
Police say the suicide bomber was wearing a police uniform, which allowed him to gain access to the bus.
A purported Taliban spokesman, Zabillah Mujahid, claimed responsibility for the attack.
The attack is the second suicide bombing targeting Afghan security forces in the past four days. On September 29, a similar attack against an Afghan Army bus in Kabul killed 30 people, mostly soldiers.
A U.S. military vehicle damaged by insurgents near Kandahar (epa)
HOMEGROWN OR IMPORTED? As attacks against Afghan and international forces continue relentlessly, RFE/RL hosted a briefing to discuss the nature of the Afghan insurgency. The discussion featured Marvin Weinbaum, professor emeritus of political science at the University of Illinois at Urbana-Champaign, and RFE/RL Afghanistan analyst Amin Tarzi.
LISTENListen to the entire briefing (about 83 minutes):
Real Audio Windows Media