NATO has reported a spike in Russian military activity at sea and in NATO and other western European countries' airspace as tensions have mounted over Ukraine. Here, a Russian military long-range bomber aircraft flies in international airspace on Oct. 29. Royal Air Force/AP hide caption

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Iraqi Yazidi women who fled the violence in the northern Iraq take shelter in the city of Dohuk on Aug. 5. The Yazidis, are a small community that follows an ancient faith and have been repeatedly targeted by jihadists. Yazidi leaders say several thousands members of the community have gone missing in recent months. Safin Hamed/AFP/Getty Images hide caption

itoggle caption Safin Hamed/AFP/Getty Images

American Ryan Boyette, left, works with Yassin Hassen, right, in an interview with a rebel in Sudan's Nuba Mountains. Boyette started the Nuba Reports website in 2011 and recruited Hassen to join as a citizen journalist. Alan Boswell/MCT via Getty Images hide caption

itoggle caption Alan Boswell/MCT via Getty Images

Five ambulances, donated by the U.S. to help combat Ebola, are lined up after a ceremony attended by Sierra Leone's president, Ernest Bai Koroma, in Freetown on Sept. 10. Michael Duff/AP hide caption

itoggle caption Michael Duff/AP