Islamic State jihadis have killed 'at least 500' Yazidis and buried them in mass grave, it has been claimed.
Mohammed Shia al-Sudani, Iraq's human rights minister, said the Sunni militants had also buried alive some of their victims, including women and children.
Some 300 women were kidnapped as slaves, he added.
It comes as the United States carried out new air strikes and aid drops as President Barack Obama vowed to help rescue thousands of civilians besieged by jihadists on an Iraqi mountain.
Obama gave no timetable for the first U.S. operation in Iraq since the last American troops withdrew three years ago and put the onus on Iraqi politicians to form an inclusive government and turn the tide on jihadist expansion.
U.S. forces hit out on the campaign's second day to protect members of the Yazidi minority, many of whom have been stranded on Mount Sinjar since they fled IS attacks on their homes a week ago.
U.S. forces 'successfully (conducted) four airstrikes to defend Yazidi civilians being indiscriminately attacked' near Sinjar, the United States Central Command, which covers the Middle East, said in a statement.
In the first strike at 3.20 on Saturday, 'a mix of U.S. fighters and remotely piloted aircraft struck one of two ISIL armored personnel carriers firing on Yazidi civilians near Sinjar,' the statement said.
After following the remaining vehicle, a second pair of strikes, hit two more armored personnel carriers and an armed truck about 20 minutes later.
Another at around 7pm struck an armored personnel carrier also in the Sinjar area.
U.S. and Iraqi aircraft have also sent planes to deliver food and water to the thousands of people - many of them Yazidi civilians who are stranded on the mountain.
Another U.S. airdrop, announced by Centcom late Saturday, sent 3,804 gallons of water and more than 16,000 packaged meals to the besieged civilians.
Obama said on Saturday: 'The United States can't just look away. That's not who we are. We're Americans. We act. We lead. And that's what we're going to do on that mountain,'
It was also announced this morning that a British military aircraft has made its first airdrop of humanitarian aid in Iraq.
The Ministry of Defence confirmed that the plane had completed its mission overnight.
The airdrop comes after Foreign Secretary Philip Hammond announced 'a continuing drumbeat of airdrop operations' around the Sinjar mountains in the north of the country, where thousands of people from the Yazidi minority religious group have been trapped.
Two Royal Air Force (RAF) C-130 transport planes took off from Britain on Saturday carrying reusable filtration containers filled with clean water, tents, tarpaulins and solar lights that can also recharge mobile phones.
French Foreign Minister Laurent Fabius was expected in Baghdad and the Iraqi Kurdish city of Arbil later today for talks with his Iraqi counterpart Hoshyar Zebari and Iraqi Kurdish president Massud Barzani.
He will also oversee the delivery of humanitarian aid to civilians who have fled the advance of the Islamist fighters.
Amid reports that children and elderly among them were already dying, Obama justified the decision to intervene on Thursday with the risk of an impending genocide against the Yazidis.
Yazidi MP Vian Dakhil, whose poignant appeal in parliament this week made her the public voice of her community, said time was running out.
'We have one or two days left to help these people. After that they will start dying en masse,' she told AFP yesterday.
The Yazidis, who worship a figure many Muslims associate with the devil, are a small and closed community - one of Iraq's most vulnerable minorities.
The U.S. strikes on Friday prompted a top Kurdistan official to say the time had come for a fightback - but there was no immediate sign that was happening.
Security sources and a local official said the bodies of 16 Sunni extremists killed in Makhmur, where IS positions were bombed on Friday and fighting with Kurdish peshmerga also took place, had been buried nearby on Saturday.
Federal and Kurdish officials, who had been at loggerheads since IS fighters launched their offensive exactly two months ago that has brought Iraq to the brink of partition, have said they were now working together and with U.S. advisers.
However, it remained unclear how much longer and how much deeper inside Iraq U.S. warplanes would intervene, and Obama stressed the real game-changer would be the much-delayed formation of an inclusive government.
Until then, he said, 'it is very hard to get a unified effort by Iraqis against' IS.
Many Iraqis see Prime Minister Nuri al-Maliki as partly responsible for the conflict by institutionalising sectarianism.
Washington, Tehran, the Shiite religious leadership and much of his own party have pulled their support but he has dug his heels in and apparently not yet given up on seeking a third term.
Grand Ayatollah Ali al-Sistani, Iraq's most revered Shiite cleric, on Saturday alluded to Maliki when he complained 'there were some people who do not want the good of the country.'
He was being quoted, after a meeting in the city of Najaf, by Chaldean Catholic Patriarch Louis Sako, whose community was displaced this week.
Up to 100,000 Christians were forced to flee from their homes in a matter of hours on Thursday, completely emptying the country's largest Christian city Qaraqosh of its population.
Among the hundreds of thousands of people who fled their homes in northern Iraq were several other minorities such as the Shabak and Turkmen Shiites.
UNESCO chief Irina Bokova called it an 'emerging cultural cleansing'.
Obama said he was confident the U.S. could prevent IS fighters 'from going up the mountain and slaughtering the people who are there' but added the next step of creating a safe passage was 'logistically complicated'.
The International Rescue Committee (IRC) is providing emergency care to around 4,000 people who crossed safely into neighbouring Syria.
'They suffer from dehydration, sunstroke and some of them are seriously traumatised,' the IRC's Suzanna Tkalec told AFP, adding that many had walked all day for several days.
Separately, U.N. Secretary General Ban Ki-moon called 'for reason and wisdom to prevail' and for politicians to form a government 'acceptable to all components of Iraqi society' to confront the threat from IS.
Iraq's parliament has been deadlocked on chosing a new prime minister following elections in April.
© Associated Newspapers Ltd.