At least 200 people have been killed in a series of bombings apparently aimed at a Kurdish religious minority group in northern Iraq, officials say.
Members of the Yazidi sect had been targeted before the blasts
Some 200 more were reported injured as at least four blasts hit areas home to the Yazidi sect near the city of Mosul.
The deadly attack was one of the most lethal insurgent strikes in more than four years of war in Iraq.
The US called the bombings "barbaric", while a Kurdish official said Baghdad had failed to protect the Yazidi.
In a statement, the White House insisted US forces and the Iraqi government would continue to "beat back" the "vicious and heartless murderers".
The BBC's Richard Galpin, in Baghdad, says that with the Americans concentrating on their military effort in the capital, officials fear the insurgents are moving into new areas where they can attack so-called soft targets.
A spokesman for the Kurdistan regional government, a semi-autonomous authority which governs three northern Iraqi provinces, described the Yazidi as a "threatened minority" and said Kurdish forces might have protected them from harm.
"We would certainly be able to improve security if we were allowed to operate in that area," Khaled Salih told the BBC.
"But because of the inaction of the government in Baghdad and their inability to protect the population they are suffering the way they are now," he added.
Tuesday's co-ordinated bombings in the villages of Qataniya and Adnaniya involved a fuel tanker and three cars, officials said.
"My friend and I were thrown high in the air. I still don't know what happened to him," Khadir Shamu, a 30-year-old Yazidi, told the Associated Press news agency.
KEY FACTS: THE YAZIDIS
Religious sect found in northern Iraq, Syria and the Caucasus
Number about 500,000 worldwide, but largest number in northern Iraq
Doctrine is an amalgam of pagan, Sabean, Shamanistic, Manichean, Zoroastrian, Jewish, Christian and Islamic elements
Yazidis believe in a Supreme God, but do not believe in evil, sin, hell or the devil
Violation of divine laws can be expiated by metempsychosis, or the transferring of a soul from one body to another
Principal divine figure, Malak Taus (Peacock Angel), is the supreme angel of the seven angels who ruled the universe after it was created by God
The mayor of Sinjal, a nearby town, said he expected the final death toll to rise.
"We are still digging with our hands and shovels because we can't use cranes because many of the houses were built of clay," Dhakil Qassim told AP.
"We are expecting to reach the final death toll tomorrow or [the] day after tomorrow as we are getting only pieces of bodies.
Tensions between the Yazidi sect and local Muslims have grown since a Yazidi girl was reportedly stoned by her community in April for converting to Islam.
The sect is due to vote later alongside other Kurds outside the Kurdish autonomous region in a referendum on joining the grouping.
Correspondents say the planned referendum makes northern Iraq's Kurds a target for politically-motivated attacks.
Yazidis worship an archangel, sometimes represented by a peacock figure believed by some Christians and Muslims to be the devil.