Private TV stations in Afghanistan have broadcast a video appearing to show a female German aid worker who was kidnapped in Kabul on Saturday.
The woman, who looked pale and whose head was covered with a white scarf, identified herself as Christina Meier.
Speaking in the local language Dari, she said: "I am OK".
A turbaned man in dark glasses then appeared, and said Mrs Meier would not be harmed, before calling for the release of "innocent prisoners".
The names of these prisoners would be sent to television stations later, he said.
"We are not the Taleban, we are not bad people," he added.
Mrs Maier's ID card was also shown in the video.
It is unclear who the armed men who abducted the woman are
The BBC's Charles Haviland, in Kabul, says that a criminal gang is suspected of carrying out the kidnapping, and that a police search operation is under way.
Mrs Meier is the first foreigner to be abducted in the city for more than two years.
The aid worker, in her 30s, works for a Christian organisation called Ora International.
Police fired at the kidnappers' car as it sped away but missed it, hitting a taxi instead and killing its driver.
Saturday also saw four Afghan engineers abducted while working on a construction project in Kandahar province in the south.
Our correspondent says that although there have recently been several bomb attacks in Kabul, kidnappings are rare in the capital.
The last time a foreigner was abducted in the city was in 2005.
The victim, an Italian woman, was released after a few weeks by the kidnappers, said to have been a criminal gang.
The incident comes amid efforts to free 19 South Korean aid workers kidnapped by the Taleban in central Afghanistan.
In addition to the South Korean aid workers, Afghan officials are also trying to secure the release of a German man kidnapped from Wardak province in June.