Militants have threatened to kill three United Nations workers being held hostage in Afghanistan, unless all Taliban and al Qaeda prisoners are released from US custody.They are also demanding that foreign forces withdraw from Afghan territory. And they have told the UN to cease its operations there. A deadline of Wednesday has been set. Annetta Flanigan from Northern Ireland was shown on a video broadcast on Arabic TV channel Al Jazeera, alongside her colleagues from the Philippines and Kosovo. In the hands of the Army of Muslims, a group thought to have strong Taliban links, they had been helping to organize Afghanistan’s first presidential election, which was held earlier this month. But the trio were snatched from their UN vehicle in rush hour traffic in Kabul on Thursday. The kidnappings have stoked fears that militants in Afghanistan may be copying tactics used by insurgents in Iraq.