Taliban-linked militants threatened Saturday to execute three foreign U.N. workers kidnapped in Kabul (search) unless British troops withdraw from Afghanistan and Afghan prisoners are freed from U.S. custody in Guantanamo Bay, Cuba.

Armed men kidnapped the three — Annetta Flanigan of Northern Ireland, Filipino diplomat Angelito Nayan and Shqipe Habibi of Kosovo — in Kabul on Thursday, stirring fears that Afghan militants were copying the bloody tactics of their Iraqi counterparts.

A spokesman for the Taliban (search) splinter group Jaish-al Muslimeen, or Army of Muslims, said video of the hostages, all of whom were working on Afghanistan's landmark presidential vote, would be sent to an Arab television channel "in two or three days."

"If these countries don't agree to our demands, we will do the same thing as the mujahedeen are doing in Iraq," Ishaq Manzoor told The Associated Press by satellite telephone.

"We may kill them if we could not get a positive response," he said, adding that he was speaking from near the Afghan-Pakistan border.

In the clearest indication that the claim of responsibility could be genuine, a Western official in Kabul said British officials and relatives had identified one of several 16-digit ID numbers supplied by the group as fitting Flanigan's credit card.

"It's definitely hers," said the official, who spoke on condition of anonymity.

Naveed Moez, an Afghan Foreign Ministry spokesman, also said government sources had "confirmed" Jaish-al Muslimeen's claim of responsibility, but didn't elaborate.

Other Afghan officials, however, said it was still unclear whether militants, renegade warlords or criminals were responsible.

"We don't know exactly who they are," President Hamid Karzai said Saturday after meeting with NATO commanders in Kabul. "Let's hope the U.N. workers are safe and sound, and we are working very hard to bring them back to their families."

NATO and U.S. troops and Afghan security forces have mounted extra patrols and roadblocks in and around Kabul since the election workers were forced from their clearly marked U.N. car into a black sports utility vehicle on a busy street.

Prime Minister Tony Blair did not immediately comment on the demand that Britain withdraw its 1,700 troops from the NATO force in Afghanistan. British soldiers serve under U.S. commanders hunting Taliban and Al Qaeda militants mainly in the south and east of the country.

Police detained seven suspects for questioning Friday, but said they had found no links to the abductions. Three of the suspects picked up in the Kabul area were armed and wore military uniforms — matching witness descriptions of the kidnappers.

Officials say the kidnappers' vehicle was seen heading toward Paghman, a valley west of Kabul with a reputation for banditry, but one suggested that the victims might still be in Kabul.

Staff of aid agencies have been ordered to restrict all but essential movements around Kabul. On Saturday evening, NATO troops positioned on a hilltop in the center of Kabul used night-vision equipment to scan the city for signs of trouble.

Earlier, Afghan police accidentally shot a U.N. driver at a checkpoint in the west of the city, when another car failed to stop at a checkpoint. The victim was in stable condition after treatment at a NATO military hospital, a U.N. spokesman said.

On Friday night, two men opened fire on an American patrol in the city, slightly wounding one soldier in the foot, a NATO spokesman said.

On Oct. 23, a suicide attacker killed an American woman and an Afghan youngster and injured three Icelandic soldiers.

The violence threatens to overshadow preparations to install Karzai as the country's first popularly chosen leader after he secured a majority in the Oct. 9 vote.

With investigators still compiling their reports into fraud allegations, election officials said no official announcement of the result was expected before Tuesday.