The Awakening militias have been credited with helping reduce violence
The head of a leading US-allied Sunni militia group in Iraq has been arrested in a joint Iraqi-US operation.
Nadhim al-Jubouri and his two brothers were arrested at their home in the town of Dhuliuya "under the charge of terrorism", the US military says.
Nadhim al-Jubouri is a leader in the Awakening Councils, US-sponsored groups that helped cut violence in Iraq after turning against al-Qaeda.
The charges reportedly date back to when he was fighting against the US.
Iraq's Shia-dominated government took over responsibility for supervising the mainly Sunni Awakening militias from the US military on 1 April.
Many of the Awakening members had been fighting against the Americans but joined forces with them in 2006 to take on al-Qaeda.
Awakening leaders have complained that they have been subjected to growing attacks from insurgents recently and that the government is falling behind in paying their salaries.
Mr al-Jubouri's arrest is the latest in a number of recent detentions of Awakening members.
'Charge of terrorism'
"Members of the Iraq National Police with coalition advisors arrested three individuals," Derrick Cheng, a U.S. military spokesman in northern Iraq, said, Reuters news agency reports.
Last month nine people were killed in an attack on an Awakening militia
He said the police had warrants for Mr al-Jubouri and his brothers "under the charge of terrorism".
The deputy governor of the province of Salahuddin said that local people had brought charges against Mr al-Jubouri for the murder of their relatives at a time when he was fighting with al-Qaeda, Reuters reports.
Last month a suicide bomber attacked an Awakening militia group in Iraq, killing at least nine people.
In March, the arrest of a leader of one of the councils in Baghdad sparked clashes between militiamen and government forces.