Zemarai Bashari, an interior ministry spokesman, said that Afghan authorities have launched a search operation.
"It is not clear who the kidnappers are but we are looking for them," he said.
Mirajuddin Pattan, the governor of Ghazni, blamed the abduction on Taliban fighters and said that the former commander of Hezb-e-Islami, an anti-Soviet faction of the 1979-89 conflict now loyal to the Taliban, was behind it.
"This the work of the Taliban," he said.
Zabihullah Mujahid, a Taliban spokesman, said that he could not confirm their involvement.
"We are trying to establish contacts with our men in Wardak. At this stage it is not clear if our men are behind it," he said.
Adrian Edwards, a UN spokesman in Kabul, said the Germans' employers were unkown.
"We don't have any idea who they are working for," he said.
A German and his Afghan translator were kidnapped in southwestern Afghanistan in June and released after a week.
The Taliban issued Berlin with an ultimatum in March to withdraw its troops from Afghanistan.
Meanwhile, a suicide bomber blew himself up on Thursday outside a police office in northern Afghanistan, killing at least one civilian and wounding 27.
General Aqa Nur Kyndoz, a police chief, said that the explosives were detonated outside the provincial police headquarters in Faizabad, the capital of Badakhshan province.
"One civilian was martyred and 27 others were wounded in the suicide attack," he said.
"Eight of the wounded are reported to be in critical condition."
Kyndoz blamed the attack on "enemies of peace," a term often used by Afghan officials, referring to Taliban fighters.
Northern Afghanistan has been relatively peaceful compared to the south and southeast, where Taliban attacks happen almost daily.
Nato forces said that they were "not directly involved" and had no soldiers near the blast site.