Samim Khpalwak, spokesman for the provincial governor, said the explosion Tuesday morning struck the city of Kandahar, the capital of Kandahar province. Authorities initially believed a car bomb caused the explosion, but later said they were unsure what happened.
Qayyum Pokhla, the head of Kandahar's regional hospital, says the blast killed three people, including two police officers and one woman. He said the explosion wounded 17.
No group immediately claimed responsibility for the attack.
Kandahar is the heartland of Taliban insurgents and the city was the capital of the extremists' government from 1996-2001.
Attacks on Afghan security forces have intensified in recent weeks as the insurgents mount their annual summer offensive.
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