Twin suicide bombings killed 48 people on Sunday, including dozens from a government-backed, anti-al-Qaida militia who were lined up to get their paychecks near a military base southwest of Baghdad, Iraqi officials said.

The bombings were the deadliest in a series of attacks across Iraq Sunday that were aimed at the Sons of Iraq, a Sunni group also known as Sahwa that works with government forces to fight al-Qaida in Iraq. The attacks highlighted the stiff challenges the country faces as the U.S. scales back its forces in Iraq, leaving their Iraqi counterparts in charge of security.