KABUL, Oct 30: A breakaway Taliban group claiming to hold three UN workers threatened on Saturday to execute them unless foreign troops withdraw from Afghanistan and condemn its "invasion" by US-led forces.

"Our demand is the invader countries that these people belong to should withdraw their troops from Afghanistan and rethink their policies towards Afghanistan," Mullah Mohammad Ishaq, a spokesman for the Jaishul-Muslimeen, told AFP by phone.

The abducted UN workers are a British-Irish woman, a Filipino man and a woman from Serbian province of Kosovo.

When it was pointed out to Ishaq that neither Serbia nor the Philippines had troops in Afghanistan, he replied: "Their countries should condemn the invasion by other countries of Afghanistan.

"If they don't do so, we will kill the hostages."

In a related development, extremists claiming to have kidnapped the three UN workers in Afghanistan have released one of the hostages' credit card numbers, offering the first proof that they are behind the kidnappings, a Western official close to the investigation said on Saturday.

"The credit card number corresponds to a Barclay's bank (card) belonging to Annetta Flanigan (a British-Irish national)," the official said.

A splinter group of the Taliban, on Saturday issued two numbers to several media organisations which they said were the 'identity card numbers' belonging to two of the hostages.

The first turned out to be Ms Flanigan's credit card number, while the second has not yet been independently verified.