At the same time, an important sheikh from the western province of Al Anbar said tribal fighters had killed 34 mostly foreign Al Qaeda fighters and arrested 40 more in a week-long drive against militant infiltrators.
Police in the northern town of Tall Afar said an attacker ran a lorry laden with explosives into a house being used by soldiers as an observation post, killing four soldiers and 10 civilian bystanders.
"This army post was set up after the last battles of Tall Afar in spring. It's not well guarded and that's why there was a lot of casualties," said Tall Afar police chief Brigadier General Sabah Al Mohammedawi.
Defense spokesman Ibrahim Shakr said the blast followed a similar suicide attack Thursday on Tall Afar military recruitment centre that had killed two people and wounded 11.
Last month, a suicide bomber wearing an explosive belt killed 21 people in a fuel queue in the restive northern town, which was once known as a haven for Sunni insurgents opposed to Iraq's US-backed coalition government.
In March, US President George W. Bush praised a US-led security operation designed to regain control of the town and boasted that Tall Afar "is today a free city that gives reason for hope for a free Iraq."
Since then, however, violence has returned to Tall Afar even as it raged on across Iraq, pitting Sunnis versus Shiites, Arabs versus Kurds and insurgents against government and US troops.
Iraqi and UN officials say more than 100 Iraqis are killed every day.
Saturday, a salvo of five mortar shells slammed into a row of houses in the village of Asriya, near Hillah, the capital of Babil province, south of Baghdad, killing two civilians and wounding four, police said.
In nearby Mahawil, a bomb exploded outside the house of a Shiite tribal sheikh, wounding one of his children and damaging the building, while a joint US-Iraqi security operation rounded up five suspected insurgents.
In Anbar, Sheikh Abdel Sattar Baziya, head of the Abu Risha clan and chair of the provincial tribal council said: "The sons of the tribes have killed 34, mostly foreigners, in their campaign over the last few days." Another 40 people were detained and handed to the authorities, he said.
Baziya said operations are largely over for now after tribal forces also secured the dangerous, bandit-infested highway across the desert from Jordan.
Other security operations were underway in Baghdad, Baquba, Tikrit and Kirkuk. Two bakers were shot dead by suspected Islamist extremists in western Baghdad, where the profession is largely a Shiite preserve and is despised by some Sunni militants as an inappropriate job for a man, police said.
Officers also found the bodies of five tortured murder victims in an east Baghdad suburb which US officers say is a hunting ground for death squads linked to radical Shiite cleric Moqtada Al Sadr's Mahdi Army militia.
Baghdad police found more than 50 unidentified corpses scattered around the Iraqi capital Saturday, an interior ministry official said. Another three bodies were fished out of the river downstream from the capital in the village of Suweira.
More than 50,000 Iraqi and US troops are deployed around Baghdad in support of Operation Together Forward, a bid to quash a wave of brutal sectarian violence that observers warn is the biggest threat to Iraq's integrity.
After Baghdad, the deadliest violence of recent months has been in the neighboring province of Diyala, where many hundreds of civilians have been slaughtered in deadly turf war between Sunni and Shiite gangs.
Iraqi army Major General Shakr Al Kaabi said his men had killed two gunmen and arrested 40 suspected insurgents after a gunbattle in the provincial capital Baquba, three days into a major security operation.
Meanwhile, the streets of the northern oil hub of Kirkuk were deserted as Iraqi authorities imposed a curfew until Sunday morning, launching an operation to hunt for weapons and rebels in house-to-house searches.
"So far 150 Iraqis have been arrested. They are suspects or wanted persons. The operation also led to the confiscation of 250 weapons and seven suspect cars," said Major General Shirko Shakr, commander of Kirkuk's police.
© 2006 Agence France-Presse