Violence by Sunni extremists against Shiites is common in Pakistan, a Muslim country dominated by Sunnis but home to a sizeable Shiite minority. Although attacks by Shiites against Sunnis do occur, such violence is not as prevalent.
Sunni extremist groups such as al-Qaeda and the Taliban often believe Shiites are infidels and that it is permissible or even praiseworthy to kill them. The emergence of those groups in the country over the last 10 years has added to the frequency and viciousness of attacks against Shiites.
Pakistan has seen hundreds of suicide attacks over the last five years, mostly by militants in the northwest close to the Afghan border who have given haven to al-Qaeda operatives and insurgents fighting in Afghanistan.
The army has responded with several offensives, but have had limited success in a country where extremists have significant support among the population.