According to an Associated Press report, the 26-year-old woman is the third US citizen to have been kidnapped by the militant group. Neither her family nor US officials have decided to identify her for safety reasons. The woman was working with three humanitarian groups in the volatile West Asian country.
The ISIS recently beheaded a 40-year-old American freelance journalist after kidnapping him in November 2012. The journalist, James Foley, who had worked in a number of conflict zones in countries like Iraq, Libya and Syria, was kidnapped by four militants in northern Syria.
The Islamic State released a video of Foley's beheading and also warned to kill another American journalist Steven Sotloff if the air strikes continued.
The Islamic State recently threatened to kill American hostages to avenge the continuing air strikes in Iraq against militants advancing on Mount Sinjar and Irbil, the Kurdish capital.
Another American, Douglas McArthur McCain, was reportedly killed in Syria. The circumstances of his death were, however, unclear.