(AP Photo/Saurabh Das)
Meanwhile, the Taliban said negotiations for the release of 19 remaining South Korean hostages have failed.
The abduction of the 31-year-old German woman, who works for a small Christian aid organization along with her husband, prompted police in Kabul to shoot at the speeding getaway car, killing a nearby taxi driver.
The assailants had pulled up to the barbecue and fast food restaurant in a dark gray Toyota Corolla, and one of the men went inside and pretended to order a pizza, said intelligence officials investigating the abduction.
They said two other men waited outside, while another remained in the car.
The man in the restaurant pulled out a pistol, walked up to a table where the German couple was sitting, and took the woman outside, the officials said on condition of anonymity because of agency policy.
The woman works for the Ora International aid group, based in the central German town of Korbach, said Ulf Baumann, a spokesman for the organization.
Baumann did not further identify the woman, but said she spoke fluent Dari and had worked for the group in Kabul since September, along with her husband, who is also German. Her husband was with her at the time and saw the kidnapping, Baumann said.
According to the organizations Web site, Ora International concentrates its efforts in Afghanistan on health issues and HIV/AIDS awareness.
U.N. staff in Kabul were told to restrict their movements Saturday as authorities investigated the abduction, a U.N. official said on condition of anonymity because he was not authorized to speak on security matters. Other foreigners were also placed under tight security.
Germany's Foreign Ministry confirmed the kidnapping and said they were working with Afghan officials toward a resolution.
The latest kidnapping comes amid heightened fears of abductions, after 23 South Koreans and two Germans were taken hostage in separate incidents last month in central Afghanistan.
One of the German men has been shot to death. The other remains in captivity.
Taliban militants killed two of the South Koreans and released two others after face-to-face talks with South Korean officials.
A Taliban spokesman, Qari Yousef Ahmadi, said the group's demands for the release of the remaining 19 South Koreans remains the same -- a swap for Taliban prisoners, which the Afghan government has ruled out.
"We're still ready for more negotiations if the Korean side is willing to meet our demands ... the exchange of prisoners," he said.