Rescuers dug through the rubble of bomb-flattened buildings in a northern Iraqi village on Wednesday as residents, many dazed and crying, looked for loved ones after suicide attacks that killed more than 200 people.
Reports tonight said the death toll may be as many as 250.
The US military said al Qaeda was the "prime suspect" in the overnight co-ordinated truck bombings that hit residential areas of members of the minority Yazidi sect, who are viewed by Sunni militants as infidels.
US officials have said they feared al Qaeda would launch a "spectacular" strike on civilians in the weeks leading up to mid-September, when the US Congress is due to receive a progress report on the military and political fronts in Iraq.
The US military launched a major new offensive in Iraq this week in a bid to thwart attacks by al Qaeda and Shi'ite militias. The operations are focused on the farmlands and villages around Baghdad that have been havens for militants.
In scenes reminiscent of an earthquake zone, bodies lay in the street covered in blankets amid the shattered ruins of clay-built houses. The buildings, mostly one-storey structures, had been completely razed.
"This is a catastrophe that cannot be described in words," said the governor of Nineveh province, Duraid Kashmoula, adding that more than 200 people were killed and 300 wounded.
He said he believed the toll could rise as many were believed buried beneath the rubble that bulldozers were trying to shift. Many people were listed as missing. Mr Kashmoula declared the area a disaster zone and asked for central government help. When he toured the scene he was besieged by people pleading for help in finding loved ones.
"The scale of the destruction is unimaginable," said another visitor to the scene, a regional government official.
The official said attackers driving truck bombs made more lethal by cargos of pebbles struck the villages of Kahtaniya and al-Jazeera west of Iraq's third-largest city Mosul, wreaking devastation that stunned even war-numbed Iraqis.
Television pictures showed badly burned and screaming survivors, many of them children, in hospital.
"People there were desperate looking for their relatives. Some were digging through rubble with their hands. I saw 20 bodies in the street, some of them burned," said the official.
The death toll appeared to be the highest in any one attack since November, when six car bombs in different parts of Baghdad's Shi'ite Sadr City killed 200 people and wounded 250. Car bombs killed 191 around Baghdad on one day in April.
In a fresh attack in north Iraq today, two car bombs struck a crowded market in a Kurdish area in the city of Kirkuk, killing five people and wounding 30, police said.
Iraq's political leaders, including Shi'ite Prime Minister Nuri al-Maliki and President Jalal Talabani, a Kurd, condemned the "heinous" bombings.
"This indiscriminate and heartless violence only strengthens our resolve to continue our mission against the terrorists who are plaguing the people of Iraq," US ambassador Ryan Crocker and military commander General David Petraeus, who will both deliver the progress report, said in a joint statement.
In the aftermath of the blast, authorities imposed a total curfew in the Sinjar area, which is close to the Syrian border.
Yazidis are members of a pre-Islamic Kurdish sect who live in northern Iraq and Syria and say they are persecuted because of their beliefs. They tend to stay segregated from the people among whom they live.
In April, gunmen shot dead 23 Yazidi factory workers in Mosul in apparent retaliation for the stoning several weeks earlier of a teenaged Yazidi girl who police said had fallen in love with a Sunni Arab and converted to Islam.