A group holding three foreign election workers hostage in Afghanistan is now threatening to kill them.

A man identifying himself as representing the militant group Jaish-e Muslimeen, or Muslim Army, told news organizations Saturday the hostages would be beheaded.

He reportedly offered personal information taken from the hostages' wallets as proof of his claims to have kidnapped them, although the Afghan Interior Ministry has not confirmed whether the information is authentic.

The three election workers - a Serbian woman, a Filipino man and a woman of dual Irish-British citizenship - were taken from their car at gunpoint in the capital Kabul on Thursday.

The NATO-led International Security Assistance Force, or ISAF, says it is helping local police track down the abductors.

Spokesman for the Kabul-based peacekeeping force Lieutenant Colonel Patrick Poulain says the kidnapping should not be seen as a sign of deteriorating security in the Afghan capital.

"We should remember that this is a unique event," he said. "We all need to be vigilant, but ISAF does not believe that this is an indicator of a worsening security situation."

He added that a pair of gunmen had opened fire on ISAF troops on Friday night as they patrolled Kabul's Chicken Street shopping district.

He said one soldier was lightly wounded in the incident, and that Afghan police later arrested two suspects in the shooting.

The previous week, a suicide bombing at the same location killed two people along with the bomber.