Ice covered leafs are pictured on a tree near Amstall in northern Austria, December 2, 2014. Freezing fog and rain covered parts of the region with ice, causing blocked roads due to fallen trees and closed schools for security reasons, local media report. (Photo by Heinz-Peter Bader/Reuters)

Pro-Russian rebels stand near a monument during a ceremony to honour the World War Two defenders of Donetsk from Nazi forces, in Donetsk, in this September 8, 2014 file photo. (Photo by Marko Djurica/Reuters)

A Polish Army tank takes part in the NATO Noble Jump exercise on a training range near Swietoszow Zagan, Poland, Thursday, June 18, 2015. (AP Photo/Alik Keplicz)

North Korean soldiers keep watch at the bank of the Yalu River, near the North Korean town of Sinuiju, opposite Dandong in China's Liaoning province, September 10, 2016. (Photo by Thomas Peter/Reuters)

People walk near a collapsed mosque following an earthquake in Meuredu, Pidie Jaya in the northern province of Aceh, Indonesia December 7, 2016. (Photo by Irwansyah Putra/Reuters/Antara Foto)

A biplane taking part in the Vintage Air Rally lands, in Stellenbosch, near Cape Town, South Africa December 16, 2016. (Photo by Mike Hutchings/Reuters)

Rohingya refugee sisters Nur Kaida (R) and Ruhana hug each other at their shelter at the Palongkhali refugee camp near Cox's Bazar, Bangladesh December 21, 2017. (Photo by Marko Djurica/Reuters)

A Siberian eagle owl, which can grow up to 71cm tall, is among a collection of 60 birds of prey at SMJ Falconry near Oxenhope, West Yorkshire, England. (Photo by Charlotte Graham)