KANDAHAR, Afghanistan, Aug 17 (Reuters) - A suicide bomber killed an Afghan district chief and three of his family members on Friday in their home in the southern city of Kandahar, witnesses and a police said.

Khairuddin Kaka, the district chief for Zerai, one of his teenage daughters and two of his sons were killed when the bomber blew explosives attached to his body, they said.

"The bomber knocked at the door of Kaka's house and blew himself up after the door was opened," said a policeman who witnessed the attack.

Violence has surged in the past 19 months in Afghanistan, the bloodiest period since U.S.-led troops overthrew Taliban's government in 2001.

Inspired by insurgent tactics in Iraq, the Taliban largely rely on suicide raids and roadside bombs as part of their campaign against the Afghan government and foreign troops stationed in the country.

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