The bullet-riddled bodies of the four men were found in the Jalrez district of Wardak province, some 40 kilometres from Kabul.
There has been a surge in attacks in areas surrounding the capital in recent weeks.
"Their hands were tied behind their backs and their chests riddled with bullets," Afghan army General Abdul Razaq Safi told AFP.
"They were killed by the Taliban because they worked for a foreign security company," Safi, who leads army units in the area, said from his headquarters in the neighbouring province of Logar.
Shahiduallh Shahid, a spokesman for the Wardak provincial administration, comfirmed the incident and said the men were seized by the Taliban while travelling to work from Kabul on Tuesday. He had no further details.
In a similar incident in the same area in late July, militants executed five men after alleging they worked for foreigners.
After those killings Afghan security forces last week launched a major operation in the area, killing close to a dozen insurgents, according to the interior ministry.
The Taliban warned at the start of their annual summer offensive this year that they would target Afghans working for foreign organisations.
Large numbers of local people work for Western civilian and military projects in Afghanistan, where NATO has 130,000 troops helping the Kabul government fight the insurgents.
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@Hardliner
Their crime was trying to earn a living to feed their families. Whether you realize it or not many Pakistani's owe their "living" to trade with the same "foreigners". I doubt you would be so callous if all those Pakistani's were executed for their ties to the West.
What a joke woman needs four witnesses but man can kill just for suspecting something. Such bizzare justice costed taliban global public opinion when they had the opportunity to rule Afghanistan.
Serves them well............. all is fair in love and war