BBC Middle East analyst
Four truck bombs in northern Iraq have left 250 dead, in one of the deadliest attacks since the US-led invasion in 2003. The bombings targeted the Yazidi sect, which Muslim extremists have denounced as infidel.
Iraq is home to the largest Yazidi community
Ethnically Kurds, the Yazidis are a small, ancient, heterodox sect.
Thought to number about half a million, they are to be found in Iran, Russia and Turkey, but the largest number are in northern Iraq.
Their religion is a blend of Zoroastrianism, Islam and other faiths.
Some Muslims have accused them of being devil-worshippers, since they revere an angel in the form of a blue peacock.
It is a charge the Yazidis themselves reject.
The Mosul area of northern Iraq - not far from its borders with Syria and Turkey - has long been religiously mixed.
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
Muslims, Christians and Yazidis have traditionally lived side by side in relative harmony.
But in recent months there has been tension, particularly between Yazidis and Sunni Muslims.
In April gunmen - presumed to be Sunni militants - dragged 23 Yazidi men from a bus and shot them dead.
This followed the stoning to death of a young Yazidi girl who had converted to Islam and run off with a Sunni Muslim man.
Al-Qaeda in Iraq was suspected of carrying out the bus attack, and is now the chief suspect in the truck bombings.
Minorities are especially vulnerable in Iraq's current violence
The group is reported to have distributed leaflets denouncing Yazidis as "anti-Islamic".
Al-Qaeda may also have logistical reasons for launching such attacks.
With US reinforcements in the Baghdad area, they seem to shifting the focus of their attacks elsewhere.
In addition, they may simply have seen the Yazidis as soft targets.
The violence is part of a broader pattern of sectarian tension and violence.
In the current climate, minorities are especially vulnerable. Some Christians and Yazidis have fled to neighbouring Syria.
Christian doctors, academics and other professionals have been targeted out of sectarian hostility - or kidnapped for ransom.
Once a mosaic of religious and ethnic groups who mostly coexisted peacefully, Iraq is increasingly falling prey to sectarian intolerance.