Ukraine's president Petro Poroshenko speaks at a meeting of the National Security and Defense Council (NSDC) of Ukraine on Sunday. Mykola Lazarenko/ITAR-TASS/Landov hide caption

itoggle caption Mykola Lazarenko/ITAR-TASS/Landov

Protester chant slogans in downtown Cairo, Egypt, on Sunday to mark the fourth anniversary of of the 2011 uprising that toppled President Hosni Mubarak. Several people have been killed in clashes with security forces. Hassan Mohamed/AP hide caption

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An official stands in front of relief materials at a camp for displaced people in Maiduguri in Borno State last week. The town, where many have gathered after fleeing Boko Haram attacks, is now said to be under assault from the Islamist extremist group. Reuters/Landov hide caption

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New England Patriots head coach Bill Belichick speaks during an NFL football news conference at Gillette Stadium, on Saturday in Foxborough, Mass. Belichick defended the team against allegations they had cheated by using underinflated footballs in a championship game. Steven Senne/AP hide caption

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A passerby watches a TV news program reporting two Japanese hostages, Kenji Goto, left, and Haruna Yukawa, held by the Islamic State group, in Tokyo, on Friday. Eugene Hoshiko/AP hide caption

itoggle caption Eugene Hoshiko/AP

Alberto Nisman, the prosecutor investigating the 1994 bombing of the Argentine-Israeli Mutual Association community center, talks to journalists in Buenos Aires, Argentina, in 2013. Nisman was found shot dead in his apartment on Sunday. Natacha Pisarenko/AP hide caption

itoggle caption Natacha Pisarenko/AP