In one of the day's bloodiest incidents, a suicide bomber in an explosives-rigged car killed six Iraqi soldiers he had lured from behind a checkpoint, just hours after Iraq's army said it captured the Egyptian leader of an al-Qaeda in Iraq cell in Anbar province, an anti-government stronghold.
On the same day, the US military announced the deaths of five more service members in the 44-month-old conflict that has grown increasingly unpopular at home.
Friday's civilian death toll was little changed from previous days. The UN estimates about 100 Iraqis die in violence each day, while Iraq's health minister on Thursday estimated 150,000 civilians had been killed in the war - about three times previously accepted estimates of 45,000-50,000.
At least 33 bodies were found, most the victims of roving sectarian death squads that usually torture their victims before shooting them.
Among the latest victims was a Sunni imam, Akram Jassim, 60, gunned down at the front entrance to his mosque in Mosul, 360km northwest of Baghdad, said Brigader Abdul Kerim al-Jubori, a spokesman for the provincial police.
In Friday's suicide attack, the bomber stopped his car after soldiers opened fire as it sped towards the checkpoint at about the 2pm (1100 GMT) in Tal Afar, 420km northwest of Baghdad.
The unit's commander, Colonel Abdul-Karim Jassim, was leading a group of soldiers towards the car when the driver detonated his explosives, police spokesman Brigadier Najim Abdullah said. Jassim was among those killed. Eight civilians were among the injured.
Sectarian violence is claiming the
lives of Shia and Sunni civilians
Earlier in the day, Iraq's defence ministry said its soldiers arrested the al-Qaeda in Iraq commander in the western city of Rawah, along with two deputies - a Libyan and Syrian - and nine other fighters who weren't otherwise identified.
The Iraqi government says thousands of foreign fighters have crossed the porous border with Syria, about 90km west of Rawah.
The US military said four of its most recent casualties, three soldiers and a marine, were killed in fighting or by roadside bombs on Thursday, while another marine died from a non-combat related injury on Friday.
State television, meanwhile, said the speaker of Iraq's parliament, Mahmoud al-Mashhadani, was visiting neighbouring Iran for an international conference.
Iran's Shia theocracy maintains close ties to Iraq's Shia majority, causing deep unease among Iraq's Sunni Arab minority. The US commander in Iraq has castigated both Iran and Syria, Iraq's neighbours east and west, for trying to undermine the American effort to stabilise the country.
Al-Mashhadani, a Sunni, has been a frequent critic of the US military presence in Iraq.