Security forces are searching for an Italian woman who was kidnapped in the Afghan capital, Kabul, on Monday night.
Clementina Cantoni had been working in Kabul for three years
Officials said aid worker Clementina Cantoni was forced from her car by several armed men and dragged into another vehicle.
Ms Cantoni worked for the aid agency Care International, which has called for her immediate release.
Last October, three foreign nationals working for the UN were seized in Kabul but were freed unharmed a month later.
Police in Kabul say a criminal gang has said it kidnapped the Italian aid worker. It is not clear if any demands have been made.
Officials have speculated that Ms Cantoni may have been abducted to be used as a hostage to bargain for the release of a jailed accomplice.
"We have detained several people including the driver of Cantoni's car for questioning," Abdul Jamil, director of Kabul police's criminal investigation department, told the AFP news agency.
International peacekeepers set up checkpoints in Kabul soon after the kidnapping to help police catch Ms Cantoni's abductors.
Abducted at gunpoint
Ms Cantoni was abducted on Monday evening after dropping off a colleague in a district in north Kabul.
Widows demanded Ms Cantoni's release
The attackers stopped her car at gunpoint and then forced her into their white Toyota.
"Four men carrying Kalashnikovs bashed in the window of her car and took her away," Care International director Paul Barker told the Associated Press news agency.
Ms Cantoni has been working in Afghanistan for three years and is a well-known figure in the aid community there.
She was running a project to provide food and income to thousands of destitute war widows.
"She helped us. After God, she was our hope," one widow told Reuters news agency, at a rally of several hundred widows who had gathered to demand the aid worker's release.
Care International is one of the biggest agencies operating in Afghanistan.
In a press release issued from Brussels, Care International said it "is deeply concerned and calls for Ms Cantoni's immediate release".
The BBC's Andrew North in Kabul says the kidnapping could also be part of an effort to destabilise the country by militants and factions opposed to President Hamid Karzai, in advance of September's parliamentary elections
Afghanistan has not witnessed the level of abductions seen in Iraq, but fears have been growing that foreigners could be targeted by militants.