American-backed Sunni militias who have fought Sunni extremists to a standstill in some of Iraq's bloodiest battlegrounds are being hit with a wave of assassinations and bomb attacks, threatening a fragile linchpin of the military's strategy to pacify the nation.

At least 100 predominantly Sunni militiamen, known as Awakening Council members or Concerned Local Citizens, have been killed in the past month, mostly around Baghdad and the provincial capital of Baquba, urban areas with mixed Sunni and Shiite populations, according to Interior Minister Jawad al-Bolani. At least six of the victims were senior Awakening leaders, Iraqi officials said.