BAGHDAD (Reuters) -- U.S. forces have said they opened fire on a group of fighters who could belong to a Sunni Arab patrol unit, days after the arrest of members of another unit by Iraqi forces triggered a gun battle.
The incident could further heighten tensions with the Sunni forces, who number some 90,000 and whom the U.S. military had backed to steer Iraq's Sunni Arabs away from an anti-U.S. insurgency.
The arrest of Adil al-Mashhadani, a Baghdad Sunni force leader, last week started clashes between his supporters and Shi'ite-led government forces.
The U.S. military said its planes had fired on four armed men seen planting a roadside bomb late on April 2 in the north Baghdad district of Taji, killing one of the men and wounding two others.
Initial investigations showed that at least one of the men was listed among the U.S.-backed Sunni fighters, who call themselves Awakening Councils but which the U.S. military calls "Sons of Iraq."
"Hostile acts will be engaged. While we value our Sons of Iraq brothers, these men had broken faith with their fellow Sons of Iraq, the Iraqi people, and us," U.S. Major General Daniel Bolger said in a statement.
The Awakening program, set up by U.S. forces, has been handed to the Iraqi government, which began paying the soldiers.
The guards comprise many former insurgents, who are worried the government may arrest them. How Baghdad handles them is seen as a test of sectarian reconciliation in Iraq.
"It is a message to those taking the same path as [Mashhadani's] gang has taken that they will face the same destiny," Iraqi Prime Minister Nuri al-Maliki told Iraqi state TV on April 2, referring to Mashhadani's arrest.
Mashhadani was arrested on suspicion of links to bomb-making cells, kidnappings, extortion, and Al-Qaeda.