250 reported dead most deadliest attack in Iraq since 2003

In what has been described as a coordinated attack, against members of a small religious sect, the Yazidis, in northern Iraq, four huge bombs went off.

The nearly simultaneous explosions, in three Yazidi communities near the town of Sinjar, added up to the single deadliest attack in Iraq since the U.S.-led invasion in 2003. Hundreds of wounded people were flown or driven to hospitals, overwhelming every emergency room in the region, according to George Shlimon, vice mayor of the nearby city of Dahuk.

The Yazidis are described by the Washington Post as:

The Yazidis are an ancient group whose faith combines elements of many historical religions of the region. They worship a peacock archangel and are considered Satanists by some Muslims and Christians in Iraq, a characterization they reject.

In wikipedia there is more information on their religious beliefs.