A fighter jet flies above as Ukrainian soldiers sit on an armoured personnel carrier in Kramatorsk, in eastern Ukraine April 16, 2014. Ukrainian government forces and separatist pro-Russian militia staged rival shows of force in eastern Ukraine on Wednesday amid escalating rhetoric on the eve of crucial four-power talks in Geneva on the former Soviet country's future. (Photo by Marko Djurica/Reuters)

British-based Ukrainians gather outside the Russian Embassy in London to protest against the build-up of troops in the Crimea region, on March 2, 2014. The demonstrators chanted and held banners demanding “Hands off Ukraine”. (Photo by John Stillwell/PA Wire)

Revellers take part in a zombie parade to celebrate Halloween in Kiev, Ukraine, October 31, 2015. (Photo by Valentyn Ogirenko/Reuters)

In this photo taken Tuesday, November 26, 2013 and made available Thursday, November 28, a Sumatran tiger leaps on Australia Zoo handler Dave Styles, left, as an unidentified man comes to Styles' aid in an enclosure at the zoo at Sunshine Coast, Australia. Styles who suffered puncture wounds to his head and shoulder was rescued by fellow workers at the zoo. He is recovering following surgery after being airlifted to a hospital. (Photo by Johanna Schehl/AP Photo)

A German Shepard bares its teeth during Schutzhund attack dog training at Witmer-Tyson Imports February 14, 2002 in Newark, CA. (Photo by Justin Sullivan/Getty Images)

Afghan policemen take position at the site of a suicide attack followed by a clash between Afghan forces and insurgents after an attack on a Shi'ite Muslim mosque in Kabul, Afghanistan on Friday, August 25, 2017. Gunmen stormed a Shiite mosque in the Afghan capital while worshippers were at Friday prayers, setting off an explosion that killed a security guard outside and pushing into the shrine, officials said. (Photo by Omar Sobhani/Reuters)

An Afghan man is carried out of a hospital after receiving treatment following a suicide truck bomb attack in Kabul, Afghanistan August 7, 2015. The bombings were the first in Kabul since Mullah Akhtar Mansour took charge of the Taliban last week, and followed a rare truck bomb attack in an eastern province on Thursday. (Photo by Omar Sobhani/Reuters)

A candle burns during a vigil in Aotea Square to remember victims of the Paris attacks on November 14, 2015 in Auckland, New Zealand. According to reports, over 150 people were killed in a series of bombings and shootings across Paris, including at a soccer game at the Stade de France and a concert at the Bataclan theater. (Photo by Hannah Peters/Getty Images)