Karachi is Pakistan's main port and premier metropolis, a sophisticated center of international business and commerce that served as Pakistan's first capital until it was moved to Islamabad in 1962.

However, it is also the country's crime center. Violence and the fear that Islamic militants are increasingly targeting Westerners have prompted many Americans, Britons, Germans and others to leave. Foreign consulates either have closed or have scaled down their staffs.

Early this year, the city's doctors staged a series of one-day strikes to demand police protection after 13 doctors, mostly minority Shiite Muslims, were slain in a series of attacks.

Karachi is also a center of Islamic militancy in Pakistan, a place where "holy warriors" on the run can find like-minded people willing to help with safe houses, false papers, money and protection.

The city is also notorious for criminality, especially kidnappings and sectarian murders in which extremists from rival Muslim groups target members of other sects for assassination.