The 60-year-old Danish man and the 32-year-old American woman were working for the Danish Demining Group when they were seized in northern Somalia, two Nairobi-based officials said.
They asked not to be identified because they were not authorized to speak to the media.
The woman was a former school teacher, one official said.
The demining group did not immediately answer phone calls placed to its headquarters in Denmark following the attack.
The aid workers were taken by gunmen while on their way to the airport, said Ahmed Mohamed, a police officer in the Somali town of Galkayo.
Galkyo is divided in two, a northern section under the control of the semiautonomous region of Puntland, and a southern section under the control of a a clan called Galmudug. Mohamed said the aid workers crossed into the southern side of the town and were abducted there.
The Danish Demining Group helps dispose of unexploded bombs and teaches communities about the dangers of land mines and other ordinance, according to its website. The role of the kidnapped aid workers was unclear.
The kidnapping comes only weeks after the seizure of two women working for Doctors Without Borders from a refugee camp in neighboring Kenya, as well as the kidnappings of two European tourists from Kenya's coast. Somali gunmen were suspected in those attacks.
Kenya said that it sent some 1,600 forces into southern Somalia to attack al-Shabab militants in response to those kidnappings, though it's not clear al-Shabab militants were responsible for the abductions.
The northern semiautonomous province of Puntland is generally considered more stable than most of the rest of Somalia, which is riven between pirate gangs, Islamist insurgents and militias and the weak U.N.-backed government in the capital. It has not had a functioning central government for the last 20 years.