"I must unfortunately confirm that two German nationals have gone missing in Afghanistan," German Foreign Minister Guido Westerwelle told reporters.
"There is an intensive search for them under way. We are following up on indications that they may have been the victims of a kidnapping."
The pair vanished close to the Salang Pass, a major route through the Hindu Kush mountains connecting the capital, Kabul, to northern Afghanistan. One local official suggested they might have been abducted by nomads. Taliban insurgents are not thought to be active in the relatively peaceful area where they vanished, just north of the capital Kabul.
Dozens of foreigners have been taken captive in Afghanistan since the 2001 US-led invasion ousted the Taliban from power, sparking a deadly insurgency, but most have been released unharmed, often after the payment of a ransom.
Germany forms the third-largest contingent of foreign troops in Afghanistan, with some 5,400 soldiers in the north under NATO command. An international conference on Afghanistan is due to take place in Bonn, Germany in December.
"We are aware that two Germans have gone missing somewhere between Baghlan and Parwan provinces. We are investigating the incident," said Interior Ministry spokesman Siddiq Siddiqui.
The chief of Parwan police said the pair were both men.
"According to our reports, the two German nationals went missing in the mountains of north Salang area on Friday," Sher Ahmad Maladani told news agency AFP.
"They had not informed police about their destination, they had left their driver and had climbed the mountains. Late in the Friday, the driver informed us that the Germans had not returned from the mountains."
Siddiqui, however, said the pair went missing two days ago.
Afghanistan is prized for its spectacular mountains, which offer remote trekking and mountaineering to extreme sports fanatics or aid workers already working in the poverty-stricken country.
Maladani said insurgents were not active in the mountainous area, which is snowy for most of the year. He added that a massive search by Afghan police, army and intelligence forces was under way.
But the governor of Parwan province, Abdul Basir Salangi, said he suspected the men may have been kidnapped by Kuchi nomads.
"There are some Kuchi people present in the area in which the two Germans disappeared," he said. "We suspect that these Germans have been kidnapped, we have detained a number of Kuchi men on suspicion of this."
Nomads from the Kuchi tribe are ethnic Pashtuns and a common sight on roads
in the area, travelling around with large herds of goats and camels.
Westerners are occasionally kidnapped in Afghanistan but are often released unharmed.
Two French journalists who spent 18 months in captivity were freed in June in exchange for what experts and Taliban sources said was a hefty ransom and the release of two brothers from a mafia-style, Taliban-linked group.