Tribesmen loyal to the Houthi movement perform the Baraa dance during a gathering to show support to the movement in Sanaa, Yemen, May 19, 2016. Bara or Baraa dance is one of the several traditional outdoor dances performed by men in the country of Yemen. Bara dance literally means a dagger dance, where each dancer holds a dagger. The style of the Bara dance differs from tribe to tribe. It is performed on special occasions. (Photo by Khaled Abdullah/Reuters)

This aerial picture taken on June 6, 2016, shows the scene of a collision between a freight train and a passengers train on their way between Liege and Namur, in Saint-Georges-sur-Meuse, Eastern Belgium. Investigators worked through the wreckage of a high speed train crash in eastern Belgium on Monday that killed at least three people and injured nine others. A fast-moving passenger train late Sunday slammed violently into the back of a slow-moving freight train that was travelling on the same track for reasons that remain unexplained. (Photo by Laurie Dieffembacq/AFP Photo)

A handout phptopgraph made avaiable by NASA showing Russian support personnel roll the Soyuz TMA-19M spacecraft after it landed with with with Expedition 47 crew members Tim Kopra of NASA, Tim Peake of the European Space Agency, and Yuri Malenchenko of Roscosmos near the town of Zhezkazgan, Kazakhstan 18 June 2016. Kopra, Peake, and Malenchenko are returning after six months in space where they served as members of the Expedition 46 and 47 crews onboard the International Space Station. (Photo by Bill Ingalls/EPA/NASA)

A handout picture provided by the press service of MORTON Group of Companies, show the balloon of Russian adventurer Fedor Konyukhov in the sky during his solo round-the-world balloon flight just after taking off from a spot near Northam, 96 kilometres north-east of Perth in Western Australia, 12 July 2016. Fedor Konyukhov took off from Northam on 12 July 2016 in attempt to beat the record of 13 days of American aviator Steve Fossett. (Photo by EPA/Morton Press Service)

A woman waits at a polio immunisation health centre, in Maiduguri, Borno State, Nigeria, August 29, 2016. Nigeria's military has liberated large swathes of land from Boko Haram but a ride with an army convoy, all guns firing for fear of ambush, shows how far the northeast is from normality after a brutal Islamist insurgency that has displaced millions. (Photo by Afolabi Sotunde/Reuters)

Bronze whaler shark (Carcharhinus brachyurus), caught in traditional seine net and released by fisherman, Muizenberg beach, Cape Town, South Africa on October 11, 2016. Action shots have captured fishermen trying to free a potentially deadly Bronze Whaler shark who was caught in their nets. The incredible images show the eight-foot-long 500-pound predator lunging its mouth towards the fishermen who are desperately trying to pull it back into the safety of the sea by its tail. Eventually they succeeded. (Photo by Chris and Monique Fallows/NPL)

A sculpture of Don Quixote shows him wearing the basin he mistook for the enchanted helmet of the fictional Moorish king Mambrino in Alcazar de San Juan, Spain, April 5, 2016. The arid central Spanish region of La Mancha is the setting for “Don Quixote”, the seventeenth-century novel by Miguel de Cervantes. Four hundred years after his death, references to the characters of Don Quixote, his loyal squire Sancho Panza and his beautiful lady Dulcinea abound in the surrounding villages from sweet treats to theatre productions involving livestock. Cervantes did not give away the name of the birthplace of Don Quixote, a middle-aged gentleman who becomes obsessed with chivalrous ideals. But many identify the village of Argamasilla de Alba as his hometown. The anniversary of Cervantes’ death is marked on the 23 April. (Photo by Susana Vera/Reuters)

In this March 20, 2016 photo, Maj. Mohammed Hussein, an officer with Iraq's elite counterterrorism forces, shows a photo of a slain Islamic State group militant still wearing in a suicide vest, taken during fighting that freed the city of Ramadi from IS control earlier this year. As they fled, the militants destroyed some buildings and booby-trapped others with explosives, leaving behind an empty prize for government forces retaking the city. (Photo by Maya Alleruzzo/AP Photo)