The governor of the Sinjar region of north-western Iraq has said 344 people died in Tuesday's multiple bomb attacks against the minority Yazidi community.
Large areas of the two villages have been utterly destroyed
He said another 400 people had been injured by the blasts and that he believed 70 others were still buried in the rubble of destroyed buildings.
About 600 local residents had been made homeless, the governor added.
The attacks on the two Yazidi villages near Sinjar were among the deadliest in Iraq since the US-led invasion in 2003.
Elsewhere, the US military in Iraq said it had killed 13 suspected insurgents and one civilian in a clash near the town of Tarmiya, north of Baghdad.
The Americans said they had been targeting a cell leader of the al-Qaeda in Iraq militant group.
The US military said the raid came after the death of one of its soldiers, who was killed when his patrol came under fire from a Sunni mosque in the area on Thursday.
A spokesman for the US military, Maj Mike Garcia, said its aircraft had fired a Hellfire missile at two gunmen on the roof of a nearby Sunni mosque in retaliation. The mosque sustained only minor damage, he added.
"These insurgents displayed total disregard for the community by using a mosque, a sacred place for Muslims to worship, as a sanctuary to commit their acts of terror," he told the Reuters news agency.
Plea for help
US commanders have blamed al-Qaeda in Iraq for the attacks on the Yazidi villages, saying they fitted the profile of "spectacular" strikes expected by the group during the ongoing US "surge" operation.
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
After surveying the scene of the attack on Friday, the mayor of Baaj district, which includes the villages, pleaded for help from the government and aid agencies.
"People are in shock. Hospitals here are running out of medicine. The pharmacies are empty," Abdul Rahim al-Shimari told reporters.
"We need food, medicine and water otherwise there will be an even greater catastrophe."
The Iraqi Deputy Prime Minister, Barham Saleh, ordered the ministries of defence and health to immediately send tents, medicine and other aid after touring the area.
He also said provincial officials had been given 1bn Iraqi Dinars ($807,000; £408,000) to distribute to the victims and their relatives.