Spies, militants and a mysterious assassination

The fatal shooting of two men in the heart of the Afghan capital Kabul - a city unfortunately used to violence - went almost unnoticed.

But then, the dead men had hoped to go unnoticed: according to one source, they were both carrying fake IDs.

Exactly what they were doing in Kabul, and who killed them, remains a mystery that touches upon the murky links between security services and extremist groups in the region.

Who they really were, at least, has become clear. According to sources in Pakistani intelligence and militant circles, the men were senior members of the Pakistani Taliban - a group that has killed hundreds of Pakistanis in suicide bombings and other attacks.