"The rocket attack happened minutes after the beginning of the vote and forced the voters to run away but after a while they came to the line and resumed voting," police chief of Ghazni province Khayal Baz Shirzoi said.
He put the attack on "the enemies of peace", a term used for Taliban militants.
Afghanistan's second presidential and provincial councils' election in the post-Taliban country began at 7 a.m. (0230 GMT) amid tight security and will last till 4 p.m. (1130 GMT).
Taliban militants have vowed to derail the process.
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