Islamic State militants have killed hundreds of Iraq's minority Yazidis.
They buried some alive and took women as slaves, as US warplanes again bombed the insurgents.
Human rights minister Mohammed Shia al-Sudani accused the Sunni Muslim insurgents of celebrating what he called a "a vicious atrocity".
No independent confirmation was available of an event that could increase pressure on Western powers to do more to help.
Tens of thousands of people, including many from religious and ethnic minorities have fled the Islamic State's attacks.
The US Central Command said drones and jet aircraft had hit Islamic State armed trucks and mortar positions near Irbil.
Irbil is the capital of the autonomous Kurdish region which had been relatively stable throughout the past decade of turmoil until insurgents swept across northwestern Iraq this summer.
There was a third successive day of US air strikes that were aimed at protecting Kurdish peshmerga forces as they face off against the militants near Irbil, the site of a US consulate and a US-Iraqi joint military operations centre.
The US State Department said it had pulled some of its staff from the Irbil consulate for their safety.
The Islamists' advance in the past week has forced tens of thousands to flee.
They have threatened Irbil and provoked the first US attacks since Washington withdrew troops from Iraq in late 2011, nearly nine years after invading to oust Saddam Hussein.
Accounts of the killings have come from people who had escaped town of Sinjar.
Sinjar is an ancient home of the Yazidis, a Kurdish-speaking community whose religion has set them apart from Muslims and other local faiths.
Some of the victims, including women and children were buried alive in scattered mass graves in and around Sinjar.
Consolidating a territorial grip that includes tracts of Syrian desert and stretches toward Baghdad, the Islamic State's local and foreign fighters have swept into areas where non-Sunni groups live.
While they persecute non-believers in their path,that does not seem to be the main motive for their latest push.
The group wants to establish religious rule in a caliphate straddling Syria and Iraq.
They have tapped into widespread anger among Iraq's Sunnis at a democratic system dominated by the Shia Muslim majority following the US invasion of 2003.