Both Islamic State group and Shiite militiamen have history of taking foreigners as hostages

Iraqi security forces fanned out across Baghdad on Monday searching for three missing US citizens said to have been kidnapped, the latest group of foreign nationals to be abducted in recent months.

Kidnappers have recently seized Qataris and Turks, but it has been years since US citizens were abducted, and it is Iraqis who have suffered the most from kidnappers seeking ransoms or to settle scores.