KABUL, Afghanistan – A suicide bomber struck at the heart of NATO’s operation in Kabul on Saturday, killing at least six Afghan civilians in an attack that officials blamed on the Haqqani network – a militant group the U.S. has designated a terrorist organization.

The blast, which left a bloody stain on a sidewalk just outside the sprawling headquarters of the U.S.-led military coalition, came as a senior Haqqani commander interviewed by The Associated Press vowed revenge for Washington’s decision.

The Obama administration gave the Pakistan-based Haqqani network, which is linked to the Taliban, a terrorist label Friday despite misgivings the move could further stall planned Afghan peace talks.