Eight members of the government-backed Awakening Council (Sahwa) militia have been killed in eastern Iraq, in the latest attacks against the group, Iraqi police tell Al Jazeera.
At dawn on Thursday, a group of armed men thought to be linked to al-Qaeda attacked the local Sahwa office in the village of Shereen in Muqdadiya, Diyala province.
The attack on the US-organised Sunni force came after a spate of bombings and shootings, mostly targeting security forces, left at least 50 Iraqis dead on Wednesday.
Recent attacks follow a reduction in the number of US troops in the country to less than 50,000, and come ahead of a formal end to US combat operations on August 31.
Nouri al-Maliki, Iraq's Shia prime minister, issued a statement on Wednesday's spate of attacks saying: "Al-Qaeda in Iraq, and its allies from the Baath party, have once again committed an ugly crime against innocent civilians and the institutions of the state ... to destabalise security and shake the confidence in the Iraqi security forces who are getting ready to take over security at the end of this month as the Americans withdraw."
"It seems to me that the security situation is much more fragile than both the American and the Iraqi authority would like to believe"
Fawaz Gerges, professor of international relations
The Sahwa, also known as the "Sons of Iraq", were instrumental in fighting al-Qaeda at the height of sectarian violence in 2006 and 2007.
The force has about 8,000 members in Diyala, most of whom are based in Baquba, the provincial capital.
Formal responsibility for the Sahwa was passed from the US to Iraq's government in April 2009, forming an uneasy partnership between the Shia dominated administration in Baghdad and the Sunni fighters.
The government promised to integrate 20 per cent of the Sahwa members into the police or army and to find civil service jobs for many others.
However, across Iraq, about 52,000 of the fighters are still waiting for new employment.
Politicians in Baghdad have been unable to form a new government, after elections in March failed to produce a clear winner.
The political dead-lock, compounded by the reduction of US forces to their lowest levels since the 2003 invasion, has likely contributed to recent violence.
Fawaz Gerges, professor of international relations at the London School of Economics, told al Jazeera: "It seems to me that the security situation is much more fragile than both the American and the Iraqi authority would like to believe.
"Unless a political solution is found, unless a national government is found that include all political persuasions, all political perspectives, the situation is likely to deteriorate in the months ahead."
Attacks on Wednesday included a suicide car bomb targeting the Qahira police station, located in the north of Iraq's capital, killing 15 people and wounding around 58 others and a suicide blast in Wasit province in southern Iraq which killed at least 10.