Minority sects such as the Yazidis are especially vulnerable as militants seek new targets to avoid the strict security measures clamped on Baghdad and surrounding areas to stop the violence among warring Sunni and Shiite factions.
Yazidis worship an angel figure considered to be the devil by some Muslims and Christians. Sect-members, who don't believe in hell or evil, deny that.
The Islamic State in Iraq, an al-Qaeda front group, distributed leaflets a week ago warning residents near the scene of Tuesday's bombings that an attack was imminent because Yazidis are "anti-Islamic."
The sect also has gained unwanted attention since some members stoned a Yazidi teenager to death in April. She had converted to Islam and fled her family with a Muslim boyfriend. Police said 18-year-old Duaa Khalil Aswad was killed by relatives who disapproved of the match.
A grainy video showing gruesome scenes of the woman's killing was later posted on Iraqi Web sites. Its authenticity could not be independently verified, but recent attacks on Yazidis have been blamed on al-Qaeda-linked Sunni extremists seeking revenge.
The only Yazidi legislator in the 275-seat parliament called on the government to step up protection for the country's small communities.
"The ethnic and religious minorities do not have militias while all the powerful parties have strong militias in Iraq," Amin Farhan said. "The government should protect these minorities by giving them weapons so that they can confront the terrorist groups."