The four men were officials in the judicial system in neighboring Paktika Province.
AFP quoted a Taliban spokesman as saying, "we killed them because they worked for the government."
There have been numerous cases of Taliban militants targeting officials appointed by the government of Afghan President Hamid Karzai.
The news comes amid ongoing negotiations to save the lives of 21 South Korean hostages being held by the Taliban in Ghazni since July 19.
Meanwhile, a soldier with the NATO-led force was reportedly killed and two others wounded in an insurgent attack in the eastern Konar Province on July 31. The nationality of the soldier killed was not disclosed.
(with material from AFP)