A criminal gang has claimed responsibility for the kidnap of an Italian aid worker in the Afghan capital Kabul and demanded the release from prison of its leaders, police said.

Abdul Jamil, director of Kabul police's criminal investigation department, said the gang was willing to release Clementina Cantoni, 32, who works for CARE International, in exchange for their leader Tela Mohammed and several accomplices.

"The criminal group of Tela Mohammed, who is in police custody, contacted police and claimed responsibility for the abduction of the Italian woman," Jalil told AFP on Tuesday, ruling out the involvement of Taliban or Al-Qaeda militants.

Cantoni was dragged from her car by armed men in the Qala-e-Mosa district of Kabul on Monday. Her driver, who managed to escape, was being questioned by police.

Afghan police last month arrested several members of Tela Mohammed's gang who operate in the north of Kabul. The group has since launched several deadly but failed attempts to free the detained gang members.

There has been a spate of attacks and kidnap attempts on foreigners in recent weeks in Kabul, leading to a tightening of security for the thousands of foreigners who work in the city.

Tela Mohammed and his lieutenant, Omara Khan, were believed to be involved in the kidnapping of three United Nations workers last October. The gang, suspected to have links with Islamic militants, released their hostages a month later but it was not known if any ransom was paid.

President Hamid Karzai was "disturbed and concerned" over the latest abduction, his spokesman Jawed Ludin said. He stressed the Afghan interior ministry had warned foreigners of possible incidents and advised them to be extra vigilant in some areas of Kabul.

Afghan police and NATO-led peacekeepers beefed up security and patrols. "As soon as we were informed about the abduction, we reinforced our security controls in the city, in addition to normal checkpoints and patrols," said Lieutenant Colonel Karen Tissot van Patot, spokeswoman for the International Security Assistance Force (ISAF).

CARE International said in a statement that Cantoni has been a humanitarian worker for 10 years and had lived in Afghanistan since March 2002. Since September 2003 Cantoni has managed a project which provides food and income-generating activities for 11,000 widows and their children. "CARE International is deeply concerned and calls for her immediate release," it said.

Afghan widows held a tearful protest Tuesday to call for her freedom. "If you don't give Clementina back, you can kill all of us," said Quandi Gul, 47, who joined more than 200 widows, mostly clad in head-to-toe veils. Fatma Khudabakhsh, 35, said Cantoni is "like my mother, sister and child."

Cantoni used to visit twice a week with rice, flour, beans and salt for the widows, and set up a poultry project that allowed the women to sell eggs at the bazaar, she said. Italian Foreign Minister Gianfranco Fini said a special panel had been set up to handle the latest kidnapping involving an Italian national.