Gunmen killed six people on Thursday in a raid on a government-backed Sunni militia north of Baghdad, as suspected insurgents continued to challenge Iraqi security forces while US troops pull back, officials said.
The attackers first killed two guards protecting the office of the anti-al Qaeda militia near Muqdadiya, 80 km (50 miles) northeast of the capital in Diyala province.
They then shot the other four while they slept in the middle of the night, said Sadiq Jaafar, deputy head of the Diyala provincial council.
A second simultaneous assault on another Sunni militia group in the same province was thwarted, with one attacker killed and two arrested, Interior Ministry and provincial officials said.
The attacks occurred a day after suspected insurgents launched a nationwide assault against police, killing 62 people in suicide bombings, car bomb attacks and shootings.
The assault took place ahead of the 31 August end to the 7-1/2 year US combat mission launched by former President George W. Bush in Iraq.
President Barack Obama has promised US voters to end the Iraq war and set a deadline of the end of this month for US troop numbers to be cut to 50,000 ahead of a full withdrawal next year.
US and Iraqi security officials said al Qaeda-linked groups were trying to undermine faith in the Iraqi security forces as the US military pulls back, and turns its focus toward training and assisting Iraqi police and troops.
Al-Qaeda's Iraqi affiliates are also trying to exploit political tensions caused by the failure of Iraq's political leaders to form a new government almost half a year after a national election in March.
The breadth of Wednesday's attacks showed that while weakened, the Sunni Islamist insurgency remains lethal and capable of carrying out well-organised operations.
Analysts say they doubt the insurgents can pitch Iraq back into the all-out sectarian war between majority Shi'ites and once dominant Sunnis that almost tore the country apart at its peak in 2006/07.
But Iraq, which is hoping to rebuild from decades of war and sanctions after signing major oilfield development deals with international oil firms, will likely remain a very dangerous and violent place for several years to come.
