The Afghan was a former member of the radical Hezb-e-Islami militia led by wanted former premier Gulbuddin Hekmatyar and had been offered 4,000 dollars to carry out the murder, the interior ministry announced.
Safia Amajan, director of women's affairs in the volatile southern province of Kandahar, was killed on September 25 when gunmen on motorbikes sprayed the car she was in with bullets as she went work.
"Yesterday during an operation we succeeded in capturing the killer, a former member of Hezb-e-Islami," said a spokesman for the ministry, which handles police matters.
"He has confessed that he killed Amajan. He has also confessed that the enemies of Afghanistan had promised him 200,000 afghani for her killing," Zemarai Bashary told reporters.
Government officials use the term "enemies of Afghanistan" to mainly refer to the Taliban movement.

Copyright AFP (Agence France-Presse), 2006