Romanian riot police detain a man, face covered in blood, after minor clashes erupted during a protest in Bucharest, Romania, Thursday, February 2, 2017. Brief clashes broke out between protesters and police in Romania¹s capital, as tens of thousands of people protested for the second night a government decision to decriminalise official misconduct. (Photo by Vadim Ghirda/AP Photo)

Riot police fire tear gas at demonstrators during a protest against fare hikes for city buses in Sao Paulo, Brazil, January 8, 2016. Brazilian riot police on Friday fired tear gas and stun grenades to disperse a violent protest against a rise in public transport fares in the country's largest city, Sao Paulo. (Photo by Nacho Doce/Reuters)

Protesters take part in “Artists Take Fight Against Police Murders” in New York's Times Square August 13, 2015. (Photo by Brendan McDermid/Reuters)

A man protesting the Ferguson grand jury decision to not indict officer Darren Wilson in the Michael Brown case is arrested while marching through the streets on December 1, 2014 in New York City. Brown, an 18-year-old black man, was killed by Darren Wilson, a white Ferguson, MO police officer, on August 9. (Photo by Andrew Burton/Getty Images)

Houthi followers perform the traditional Baraa dance ahead of a demonstration against the Saudi-led air strikes in Yemen's capital Sanaa August 24, 2015. The nothern-based Houthis, a Shi'ite Muslim group, took control of Sanaa last September. Arab countries intervened in the conflict in March to halt a Houthi advance into the south which caused the Saudi-backed government to flee to Riyadh from its refuge in the southern port of Aden. (Photo by Khaled Abdullah/Reuters)

People protect themselves behind a trash can as anti-riot olice fires water cannon to disperse thousands of people demonstrating following the death of Berkin Elvan, a teenage boy wounded in mass anti-government demonstrations last year, on March 11, 2014 near the Middle East Technical University (ODTU) in Ankara. Elvan's story – he spent 269 days in a coma – gripped the nation and became a symbol of the heavy-handed tactics used by police to reign in the biggest demonstrations against Prime Minister Recep Tayyip Erdogan since he came to power in 2003. (Photo by Adem Altan/AFP Photo)

A riot policeman fires into the air during clashes with opposition supporters at a rally demanding a referendum to remove President Nicolas Maduro in Caracas, Venezuela, May 11, 2016. (Photo by Carlos Garcia Rawlins/Reuters)

A National Bolivarian Police officer rescues a man who was being attacked by protesters, who then threw rocks at them, during a protest demanding food a few blocks from Miraflores presidential palace in Caracas, Venezuela, Thursday, June 2, 2016. Venezuela is seeing rising frustration with widespread food shortages and triple-digit inflation. (Photo by Fernando Llano/AP Photo)