Afghan militants killed six civilians in a botched ambush of US troops just to the south of Kabul, while to the east, militants shot dead two police academy teachers, officials said yesterday in the capital.

　　The assaults on two sides of Kabul, as well as the discovery of a bomb cache, underlined the threat facing the tightly guarded city of 4 million, which is home to thousands of foreigners and has been spared much of the violence that has wracked other parts of Afghanistan.