Part of the reconstructed Malaysia Airlines Flight 17 plane is seen prior to the presentation of the Dutch Safety Board final report on what caused the Boeing 777 to break up high over eastern Ukraine last year. Peter Dejong/AP hide caption

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Two polio cases have been reported in Ukraine, where some parents are fearful of vaccinations. Above: A child receives the diphtheria, whooping cough and tetanus vaccine in a children's hospital in Kiev. Sergei Chuzavkov/AP hide caption

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Russian workers threw contraband peaches off a truck outside the city of Novozybkov on Aug. 7. AFP/Getty Images hide caption

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In Nieuwegein, Netherlands, on Friday, relatives and friends of victims gather in front of a "hedge of compassion" made of thousands of stuffed animals during a commemoration of the victims of the Malaysia Airlines MH17 plane crash in eastern Ukraine. Michael Kooren/EPA/Landov hide caption

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Ukrainian national guardsmen practice protecting and recovering wounded comrades as American military trainers watch. Corey Flintoff/NPR hide caption

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Mikheil Saakashvili (center) is the former president of Georgia, which waged a brief war with Russia in 2008. Last month, Ukrainian President Petro Poroshenko (left) named Saakashvili the governor of Odessa, the port city in Ukraine, a country waging its own battle with Russia. The two are shown in Odessa on May 30. Mykola Lazarenko/Presidential Press Service Pool/AP hide caption

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A soldier in the Russian army posed, rifle in hand, for a snapshot at a battlefield checkpoint. Simon Ostrovsky, at right, located the same spot in Vuhlehirsk, in Ukraine's Donetsk region. VICE News hide caption

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Refugees from different cities of the Donetsk region controlled by pro-Russia separatists stay March 12 in a center for refugees in the eastern Ukrainian city of Slavyansk. The cease-fire in eastern Ukraine between Kiev's forces and pro-Russian rebels has been tenuous at best, and residents of the region continue to flee; 1.2 million have been displaced by the fighting. Sergei Supinsky/AFP/Getty Images hide caption

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A Ukrainian serviceman walks in the village of Pisky in the region of Donetsk controlled by Ukrainian forces on Feb. 26. Oleksandr Ratushniak/AFP/Getty Images hide caption

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Russian opposition leader Boris Nemtsov, who was shot dead last Friday, was one of the most outspoken critics of President Vladimir Putin. No arrests have been made in his killing. Ivan Sekretarev/AP hide caption

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Workers stand next to a gas pipeline not far from the central Ukrainian city of Poltava in June 2014. Ukraine imports much of its gas from Russia, which is once again threatening to cut off supplies in a dispute over payments. Sergei Supinsky/AFP/Getty Images hide caption

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Ukrainian servicemen stand guard on a street near a burning building after a shelling by pro-Russian rebels of a residential sector in Mariupol, eastern Ukraine, last month. Reuters /Landov hide caption

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A child plays near Russia-backed separatists in Donetsk, Ukraine, Monday. Separatists say they've begun to withdraw heavy weapons from the front line — a claim that monitors say they can't verify. Vadim Ghirda/AP hide caption

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On Sunday, thousands of people gathered in Maidan to mark the first anniversary of anti-government demonstrations that left scores of protesters dead. Geovien So/Barcroft Media/Landov hide caption

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Ukrainian troops ride on self-propelled artillery near Artemivsk, eastern Ukraine, Monday. A Ukrainian military spokesman says that separatist attacks are delaying Ukrainian forces' pullback of heavy weapons from the front line. Evgeniy Maloletka/AP hide caption

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Britain's Foreign Secretary Philip Hammond and Secretary of State John Kerry deliver a statement at a news conference in London, today. Kerry said the two were going to discuss the possibility of further sanctions against Russia amid cease-fire violations in eastern Ukraine. Neil Hall/AP hide caption

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In this photo provided by Britain's Royal Air Force, taken Oct. 29, 2014, a Russian military long-range bomber aircraft photographed by an intercepting RAF Typhoon flies in international airspace. Robyn Stewart/AP hide caption

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