The bomber detonated his deadly charge in Al-Quba, killing at least 30 people and wounding another 50, eight of them seriously, said provincial police spokesman Brigadier General Abdulkarim Khalaf al-Juburi.

The reported death toll climbed rapidly through the morning with the farming village 20km north of the much larger town of Tal Afar and the nearest emergency services.

Such attacks are increasingly common in villages, as militants flee to rural backwaters away from thousands of US and Iraqi security forces cracking down on Baghdad and other flashpoint cities under a five-month-old security plan.

Attacks elsewhere killed another 15 people in Iraq, including nine wiped out when a roadside bomb ripped through an unofficial stop for one of the battered minibuses used by thousands of people in Baghdad.

The device, hidden on the side of the road, blew up after a minibus stopped to collect waiting passengers in the Diyala Bridge neighbourhood in the southern suburbs, security officials said.

Shrapnel sprayed the area as Iraqis got on and off the minibus shortly before the main rush hour, and as others stood waiting for a different line.

The Al-Zafaraniyah hospital said nine people were killed, including a woman, and eight wounded were brought in with mainly burns injuries.

In the Sunni Arab heartland north of the capital, mortar rounds crashed through private homes, killing six civilians and wounding another 17 in the town of Dhuluiyah, the local police chief and hospital director said.

Police Colonel Mohammed Khaled said one woman was among the dead, with four women and five children wounded in an attack that seriously damaged five homes in the town centre.

Doctor Othman al-Juburi confirmed the casualty numbers as his medics in casualty struggled to cope with the limited supplies hampering hospitals' ability to treat patients across the country.

Iraq's brutal sectarian warfare and insurgency kills and maims daily despite the US military thrust against rogue Shia militias and al-Qaeda in Iraq extremists the Americans blame for most of the violence.

US forces said they killed 11 rebels and arrested 10 suspects on Monday in operations around the Tigris River Valley, the northern belt of Baghdad.

An air strike killed seven presumed fighters after US ground forces came under heavy gunfire in a raid against an al-Qaeda in Iraq emir responsible for attacks in Salaheddin province, where Dhuluiyah is located, the military said.

In Baghdad, US and Iranian officials were locked in security talks in the latest effort between the arch-foes to find ways to contain the insurgency.

A US official told AFP on condition of anonymity that the meeting was under way at the office of Iraqi Prime Minister Nuri al-Maliki in the heavily fortified Green Zone that houses the government and US embassy.

"It's at experts' level, people who are experts in the security field," said another US embassy official. "This is an Iraqi-led trilateral meeting... As far as I know, only security will be discussed."

US military also announced the death of another American soldier in Baghdad, bringing US losses in Iraq since the March 2003 invasion to 3,666, according to an AFP count based on Pentagon figures.

Another four American soldiers have been killed in attacks around Iraq's war-torn capital, the US military said on Sunday.

Two of the soldiers died of injuries sustained during combat operations on Sunday in Baghdad, the military said.

Another soldier was killed and two others were wounded in western Baghdad on Saturday, while the fourth soldier died of wounds after a roadside bomb attack alongside a military vehicle near the capital on the same day.

On July 24 the delegations of Iran and the United States, led by Kazemi Qomi and US ambassador to Baghdad Ryan Crocker respectively, were unable to agree during a landmark second meeting on ways to restore security to Iraq.

But the two countries did agree to create a tripartite security committee aimed at curbing militia activity, battling al-Qaeda and securing borders, albeit without reference to the Shia militias Iran stands accused of arming.

The US military in Iraq regularly accuses groups linked to Iran of training extremists in the war-ravaged country and supplying them with explosives capable of penetrating American armoured vehicles.

Iran denies supporting insurgent groups in Iraq.